Why do CFL bulbs not work with electronic light timers? I have triedd them with my porch light and they burn out very quickly.

Sometimes timers release a small amount of current when they're not running, which is why they are not recommended to use with CFLs. If you're intent on using a CFL, you might try a different brand, I've used a certain brand CFL with a timer light and had no problems.

I can't agree, dimmers yes but timers do not "leak" current. Is the porch fixture exposed to weather or covered?