Just to check the obvious, but how late in the day do you drink coffee or other caffeinated drinks?

Its surprising how many people tell me they're insomniacs, and then I find out they're having double strength coffees after dinner and trying to convince me that coffee doesn't affect them. My personal rule is no coffee after 2 if I want to get to sleep around 10pm. If not, I get that 'really tired, but almost twitching' feeling in bed.