I tried CFL's before all this damn "green" push. They just don't cut it in cold winter states and I believe the cold actually burns them out quicker.
Wish CFL tech would come along more WITHOUT having to be mandated on me.
Heat burns them out quicker as well. If you purchase the CFL flood lights or spot lights, they simply are a CFL enclosed in a standard floodlight/spotlight glass envelope. The heat buildup inside the glass envelope case causes the bulbs to burn out faster than a standard floodlight or spotlight.
I purchased a three pack at Costco twice before I figured out what was happening. After I installed plain CFL bulbs in the two outside canister lights above the garage door, I have yet to replace them and it has been over two years of them burning from sunset to sunrise.