Normal lifetime of non-stick teflon pans
America's Test Kitchen says that good quality nonstick pans last them about six months.

They're presumably cooking with them several times a day, so if you use it once every couple days, and are as good as they are about not doing things that'll damage the coating, you might get a few years. So your experience sounds roughly normal.

As another data point, they also quote the Cookware Manufacturers Association: "'If you get a year to a year and a half of life out of [a new nonstick pan], we think you got a pretty good deal.'" That's coming from people interested in selling pans, possibly not talking about the best quality, and with experience based on typical less-careful usage, so I'm not surprised they gave a lower number.