You can also still get done for a lot of the pre-workouts, most of them contain synephrine now instead. Basically, don't touch preworkouts anywhere near a meet - you can look up the exact half-lives if you want to be exact (5 half lives is considered elimination, I give it 10) but then you run into issues with imported supps which don't list all their ingredients.
ASADA say just don't use any supplements at all.
And yeah, there isn't a banned limit on caffeine any more.