My GoreTex Danner Vipers are still waterproof after 8 years, though I re-treat the leather any time it shows signs of getting dried out. They don't get subjected to prolonged submersion and are more likely to be in wet mud than straight water. So far, so good though. After reading other posts, I'm feeling lucky.
I had a pair of "waterproof" Rocky snake boots that leaked from the the first time I wore them. It was more like I was wearing cotton socks than boots, as walking through wet grass saturated them. They got returned immediately.
Jim