Reddit held out longer than three months. I remember remarking to spez during Startup School '06 that I had noticed a recent, slight downtrend in quality. That was around the time that random photographs started appearing on the front page, and a couple weeks after the famous "Paul Graham Eats Breakfast" post. But it was far from nonsense then: the majority of front page content was still excellent. Reddit launched in late summer '05, so that's at least 8 months that it held out.