I second this. I have a D-Link Gamer Lounge (DGL-4300). This is the most stable router I've ever owned. Thumbs up on the QoS, stability and speed (GbE). If I were able to run 'uptime' on it, I believe it would say close to two years (I live in Florida, but it's on a UPS). Oh, wait:
Connection Up Time : 617 day(s), 12:04:53
My last router was a WRT54GL that decided to brick itself after about three months of DD-WRT.
I think I should agree with some of the above posts that offloading network services can help these routers, but I'm not sure. I run my own DNS and DHCP, so this router has never had to bear that load.