I usually leave a note indicating which route I am taking before I leave (you know...cuz sh1t does happen after all) and about 99% of the time that is dictated by either my mood, wind speed/direction,or all three. How many times have you flown right along with a good strong tailwind, gone a little farther than originally planned and turned for home. Creeping along at 8 mph can make you realize how far that actually is. This can actually be a dangerous thing to do if it's cold enough out, and anymore that is my only limiting factor in the wintertime since snow here is rare anymore.
As far as wind, I don't care how hard it's blowing unless it's the kind that usually comes in heavy gusts at about a 45 degree angle to my front tire. That sucks, especially when you're trying to watch your backside for traffic.