bdiddy,
I work out 5 days a week; swim, bike, run. I will say that If I smoke the night before a long swim, I will feel a *tad* sluggish, but by no means enough to have a major effect on my training. I've only done one half marathon, but I've done a few triathlons. I usually won't smoke for two or three days leading up to the event. Long runs for me during training are 6 or 7 miles, long bike rides are probably 50-60 miles or little longer, and long swims are well over a mile, close to 2 miles.