"... I've got a Marmot Essence that's 3-4 years old, but is reserved only for backpacking and wear it maybe 12 times a year. Would you consider delamination of their membrane normal wear and tear?"
Three days into an overseas adventure I discovered my eVent jacket was no longer waterproof. When held up to the sun I could see sparkles of light throughout the body and arms. It was about 4 years old.
I do 3 or 4 hikes about 10 days long each year. Most of the time that jacket was stuffed in my pack. My cadence is about 2 steps per second. That results in 120 "bounces/compressions/jostles a minute, 7,200 per hour, 72,000 per day, 720,000 per trip, 2,880,000 per year, not counting daily/weekly use for training and day hikes. 10 million "rubs" over 4 years.
It was a "2.5 layer" jacket and I had simply abraded the "1/2 layer" of tricot (think noseeum mosquito netting) and then the membrane. My new jacket cost $115 (half of the first one), weighs less (7 ounces), and is a better performer, but I'll start testing it at year 3.
A 3-Layer, 2#, $400 jacket would probably last longer.
Performance, Weight, Price. You get to pick two.