. . .once you learn how to use trekking poles, you won't be adjusting them anyway.
You will have to adjust the poles if they are used to hold up your shelter! The lengths I need for the tents I own are all longer than what I need for hiking! It's also nice to be able to shorten the poles to the max and tie them to my pack if I have to scramble using my hands or bust through brush (something I no longer do, but have in the past).
Of course, if you're just trying out poles to see if you like them, old ski poles are the most economical way to start. No point in paying for more expensive poles until you're sure you'll use them!
I've never had an adjustable pole collapse on me. That's rather surprising since I don't have a lot of hand strength and sometimes have to visit a neighbor for help opening jar lids. Both of my pole sets are the same brand (Leki), for whatever that's worth.
The poles I've used for everyday walking and day hikes are about 6 oz. heavier than the carbon fiber poles I use for backpacking. While the poles aren't part of pack weight, they are part of skin-out weight, which is what is carried on my feet and knees.