If you use a modern extremely light weight tent hard in mountain conditions I'd expect 2-3 years only. The light weight zippers and fabrics wear quickly especially in rocky habitat.
This is a bit what I'm worried about. I assume when you go for the really lightweight stuff that you end up sacrificing some longevity, no?
My current go-to tents for 3-season backpacking are a pair of Big Agnes Copper Spurs UL-1 & UL-2. I've been using both tents for 3-season backpacking for several years. They are ultralight tents so the materials are very lightweight. They are still going strong despite the flimzy appearance. I try to take care of them and avoid mistreating them. I guess it's these current ultralite tents that I think I might actually wear out because the materials are so lightweight. We shall see.
I don't think I have ever worn out a tent.
I have had a couple of cheap standup dome tents ruined by the wind. You get what you pay for. I had a Sierra Designs Origami-4 (TIPI) ruined by the wind also.
I had a North Face VE-25 (that's a bombproof expedition dome tent) ruined by a friend because he ran a stove inside the vestibule and cooked the rain fly.
After many years of service, I gave an REI Quarter Dome T-2 to my grandson. He's still using it and I expect he will get many more years out of it.
I over-stressed the zipper on a Cabelas XPG-4 tent. But that was my fault, not the tent. I've had a new zipper installed and expect many more years of service.
I have an REI Base Camp-6 tent that's several years old. I have used it many times in situations that it was not designed for and it has weathered them all.
I have owned a Sierra Designs "Clip Flashlite" tent since sometime in the '80s. It's still in like new condition, but I haven't used it much in later years. There are lighter alternatives on the marker.
I even have a couple of canvas gable tents that have been taking up room in my storage shed for several decades. But they have not been used much for a long time either.
For winter backpacking, I use a KUIU Storm Star 2P. I bought it three years ago when the traveling KUIU show came to town.
So I agree with those who have said that a good tent will last a lifetime if you take good care of it. But beware of the newest ultralite tents made with ultra light materials. I think we all have to take good care of them to make them last.