Hi TomD Hi Daisy.
Daisy I am so glad that you brought this up because I have a reputation for slaughtering sacred cows. I basically do not use nor agree with the layering concept (OR DO I???). Like others here, I was exposed to such extremes when I started out that I have always tried to be prepared for the worst, and the best.

I believe in properly fitting highly breathable aerobic travel clothes and a couple of heavy in camp pullovers. Not to get into specifics of which gear -

In the winter I ski in long underwear with a fleece jacket on top and packlite shells over the jacket and long underwear bottoms. This allows me to vent or close up and regulate temperature easily while moving and none of it absorbs moisture. Upon arrival at camp I will remove the shells, pull on goretex down bibs that fit over everything else and a large down coat with a weather proof exterior so I do not need an extra shell (to put over the big coat) and so my ski shell can fit correctly.

If I am just day skiing, I will put my Montebell UL down jacket into my pack for extra warmth if I stop for a while and it can squeeze under the outer shell if need be, but the jackets exterior can handle snow and frozen precipitation.

I hate wearing 4 layers - 3 is kind of ok depending on whether or not you have to move a lot, but 2 is awesomely free and unencumbered feeling - like the longunderwear and down bibs with built in goretex shells on my legs - warm with complete freedom of movement.

THAT SAID - My longunderwear/fuzzy jacket and shells are very adjustable without removing them so I wonder if that is "layering". If it was really warm I'd take off the fleece jacket entirely, but normally I only buy jackets with matching pit zips for ventilation, so real venting with the rain shell on is possible.

So if the layers are a couple of thin ones and a thick one - then I layer, but a lot of thin layers is very heavy - the lightest insulation there is, is a down coat with a good exterior shell. My deep winter coat weighs 40 ounces, has a thick expedition style hood, a large flap over the zipper and its Guaranteed to keep me dry under extreme circumstances. The down bibs weigh about 32 ounces. This coat and bibs over longuderwear and a fleece jacket has kept me warm at -5 in a 50 mph wind. You need the ectra warmth of a fleece jacket around your torso and it is nice to sleep in, but a stuffed jacket is less binding to sleep in than fleece.

So what does "layering" mean? and does it mean different things to different people in different climates. If seems to be too general of a statement to be a sacred cow - you might as well say - take enough clothes.

I think the problem many may have is not having an adequately warm layer - something in another order of magnitude of warmth than their other "layers". Maybe instead of 5 medium layers a light, medium and heavy layer is better.
Jim