I have a pair of GTX650 bought in 2012 still running BOINC at 100% 24/7. Air cooled, fans on Auto, no OC with an open case. Had various other GTX running for 5 years plus no problems all on Boinc or Folding@home.

Only added Team Red to the farm since starting Alt Coin mining in last year so not sure on those, but Team Green can certainly do 5 years no problems at all.