It will last for next 2 years in gaming.crossfiring is your choice.
2 years for single gtx 670 or sli 670?
crossfire do not perform well in 3d. (that is what i hear)(or their 3d is suck)
i got a gtx 670 it is pointless i go for crossfire since it will cost a lot more( need to buy 2 new card)