How do you all upgrade, or prefer to upgrade your graphics cards?
Let's say you had a pretty decent single graphics card of this generation in your rig. When the time to upgrade comes in a few years would you prefer to get another one of the same kind and sli/crossfire them together, or try to sell it off and get another single next-gen card of the same tier? Post your reasons/opinions and feel free to include your history of graphics upgrades.
I currently have an evga 780 SC and I'll probably double up on another one once I feel the need to upgrade. This is probably because I'll be too lazy to try and sell it, and it will still be good enough to be a waste just having it collect dust. Then maybe after that I'll retire the both of em and get another single gpu configuration.