http://en.m.wikipedia.org/wiki/Xbox_360
We have just passed the 7 year mark and the next only expected end 2013 somewhere. That makes it 8 years. Expect perhaps another year of games etc... before forced to upgrade to the new console.
The warranty is a year but they have an excellent exchange program.
I have had 2 of my earlier Xboxes (got 5) red ring on me way after the warranty expired. I took them into MiDigital in Edenvale (called Powercare now AFAIK) . Paid R600 and they exchanged for a brand new consoles. My 2 Elites and my Slim have never given me any problems. Was just the early Pro's that had issues.
EDIT: I was a hardcore PC gamer up until MW2 came out. I switched to console and love it. No upgrades every 6 months to keep up with latest games. No driver hell. All simple plug and play.
I still play RTS on PC though. Tried C&C on Xbox and found it clumsy.