Below is the list of "dates active" of Neverwinpoker and the forums which spun off of it, from longest to shortest.
By "active", I mean the period of time where regular new posts can be found on the site on a daily basis. For example, boris and Donkdown are still up, but neither have been active for a long time.
1) Neverwinpoker (May 2004 - November 2009): 5 years, 6 months
Reason for death: Pokernews shut down forum
2) PokerFraudAlert (March 2012 - Present): 3 years, 7 months
Still active (at least for now)
3) Boris (January 2009 - December 2011): 2 years, 11 months
Reason for death: Ian and his big chin
4) Donkdown (December 2009 - June 2012): 2 years, 6 months
Reason for death: Defections to PFA
Feel free to chime in regarding Venompoker and Marty's various failsitse. I don't have those dates. But the above 4 have been the main sites, though I am leaving out Skatz just to piss off gay sex.
DD seems like it was active more than 2 1/2 years, but that's all it had.
BTW, when I started PFA, I wasn't sure what response it was going to get. I was prepared to shut it down quickly if it didn't catch on.