I have two almost identical video cards, one I bought a year ago and one I just got a little more than a month ago. The second one died last week. The good news is a lot of card manufacturers have lifetime warranties, so its like you can resurrect it from the dead!! YAY!!
Usually its the Fan that starts making noise which is the first thing that requires it needing to be fixed or replaced. In the past I have had cards that needed new fans, and actually preferred the cards w/o fans because of this.
With the lifetime warranty, cards will last as long as you want them. In the past it appeared as though there were new generations ever six months, but I think it is slowing down some. I am thinking my two GTX 260s should last me another 3 years before I need to upgrade.