From long distance hitch hiking, hiking, and now hiking and cycle touring I have gone from super light to what I would say is regular and heavy. This has been a 40 year journey.
In my teens I hitched through Europe with only a plastic sheet and a sleeping bag. This year I put to rest my MSR Carbon Reflex 2 and finally turned away from ultralight.
Now, for hiking I use, Exped Mira II previous model: 2kg. For cycle touring I dumped the useless and super overrated Hilleberg Rogen and now use the Exped Venus II: 3kg.
Before I explain why, I confirm your astute observation: yes I am only taking about shelter. In all other things I am ultralight.
First of all, I think only a tent offers real protection no matter the weather.
I live in Japan and we get extremes of weather including typhoons. And the problem with light tents is the materials are too fragile and don't last very long. More importantly, they cannot handle very heavy or semi dangerous weather. So, unless the weather is lovely and the forecast similar, you can never climb into the tent without some worry.
Add some extra weight and you get a water column tent floor of 10,000 mm and a fly sheet of 1500. 10mm poles. You can have a tent that does not collapse in 100km winds.
To conclude, I think when it come to the shelter, some extra weight will save you money because the tent will last longer and give you peace of mind: you close your eyes at night knowing you will not wake up to imminent disaster. No matter what.
Loc: Washington State, King County
Your two criteria for moving to a heavier tent are durability and ability to hold up in severe weather.
My experience w.r.t. durability is that lightweight tents can hold up very well. To date I've hiked about 13,000 miles and the majority of that was with just two lightweight tents, both of which I still have and use. The lightweight zippers eventually need to have the zipper pulls replaced, and I just bought some spray-on stuff to hopefully rejuvenate the water resistance of my sil-nylon tent (a Tarptent Contrail), but both of them are still good tents. So --- I don't consider durability to be a major factor unless a person is particularly hard on gear.
In terms of severe weather, there are different mitigating strategies. For shorter trips and even not-so-short trips, the primary one is to be aware of weather forecasts and just get out of such weather --- hike to a trailhead and hitchhike out if necessary, and of course just don't start the trip if a hurricane or typhoon or sharknado are whatever are called for. If out in such weather, understand the dynamics of the weather system and how terrain impacts your comfort and survival. I've hiked in places where thunderstorms are a regular afternoon feature, so planning the days hike includes trying to be off of high ground at such times. Etc. When wind is a factor, it's possible that in high wind conditions one might stop hiking earlier than normal if a particularly good wind sheltered spot is discovered; I've done this a time or two.
But I've never hiked when I thought really severe weather was likely. In Florida there was some pretty severe weather coming through shortly before I started a several hundred mile trip, but it passed and I just watched forecasts pretty closely once I started hiking.
I'm NOT saying that there isn't a place for a heavy, very weather resistant tent. I'm just saying that for me, personally, there isn't.
IMHO, you are talking about fit. We can't say often enough your equipment needs to fit the wheres and whens of your backpacking trips. If you are consistently camping in places with heavy rainfall where the ground under your tent is soaked and high winds consistently then a UL 3-season tent just won't cover it. You have to bring the equipment you need for the situation you are going to face.
I still think you are bringing lightweight equipment for the situations you are facing. From my perspective lightweight backpacking is about choosing not to bring weight you do not need. UL is about only bringing the equipment you need to survive. What those actual weights are depend on the circumstances.
I certainly agree with your conclusions. The conditions I hike in are not nearly as severe as yours and a bombproof tent is very important to me. The peace of mind is worth the extra weight. You are not talking really heavy either. It probably is just converting to a mountaineering tent vs a typical lightweight backpack tent. I have gone lighter over the years, but stopped short of UL. I do admit that the cost of a UL tent has been a stumbling block.
Sorry, I aim to do more than just "survive". I prefer to maintain some level of comfort..
I think continuously bad weather is a bigger factor than any one night of bad weather. In the Sierra, I have been in very severe storms, but there were always windows of sunshine to dry out. In the Rockies, I have been in weeks of continuously wet/snowy weather and that is a different story. Also, most of my trips are above 10,000 feet and well above timberline.
Over time I have accumulated many tents, tarps and bivy sacks. I have yet to find ONE tent that does it all.
Your post is wrongly titled. You moved from light weight to RIGHT weight. (Right for you, that is.) I've also played the ultralight game, and backed off a bit.
Colin Fletcher had it right 40 years ago: Rule 1 - If you need it, take it. Rule 2 - try to take the lightest version that will still do the job you need it to do (Rule 2 is not a quote, but a paraphrase of the rest of that chapter.)
Nothing is new under the sun. Even 100 years ago and more, Nessmuk wrote, "Go light, the lighter the better so that you have the simplest material for health, comfort and enjoyment." I am sure even before him, all wanderers knew to take only that which was necessary.
Actually, many years ago I was going through my father's things (after his death), and found an old Army manual his unit had published after they finished the battle of Guadalcanal. (His regiment was brigades with a Marine unit to form the Composite Army Marine - CAM - that stayed together through Guadalcanal, Iwo Jima and Okinawa.)
Anyhow, it had tips the unit had learned while moving through the jungle on foot. Among them: take only what you need (but always take three pairs of socks), and you don't need your full mess kit plus canteen and canteen cup: take the cup, spoon, and canteen; the cup can triple as a pot, cup, and bowl. It also talked about stripping down the C-ration kits to just the food, and so forth.
Loc: Pittsburgh, Pa, USA
I have two tents (three actually, as one is a convertible).
If I know I am not going to experience heavy rains (like bping in Arizona) then I go with my light weight tent. Used it for several seasons now and it shows little sign of wear.
If I expect heavy rains then I use my other tent (SD Alpha CD). If I expect snow (heavy) then I toss in the snow fly.
I tried hammocks for a while, but found them to be a pain. Don't get me wrong, I like them, but I found it a pain trying to find two trees at the right distance, getting the "hang" right, rain coming in from either end.
Life should not be a journey to the grave with the intent of arriving safely in a well preserved body, but to skid in broadside, thoroughly used up, worn out, and loudly proclaiming Wow! What a Ride!