ohshea
Bluelighter
^the toothbrush holder is a good ide. Thats the problem w premade shots is worrying about them leaking/plunger inadvertly getting pushed down.
I've done this many times, like when I'm going to be at work or out with friends, or when I'm couchsurfing and unsure if I'll be able to sneak off to a bathroom for 10-20 minutes without someone wondering what's going on. So far I've left shots (inside a hard plastic toothbrush holder, so the plunger doesn't accidentally get pushed down) for as long as 24 hours, and I don't seem to have suffered any adverse side effects, and seem to get just as high as if the shot was "fresh." I use bottled water and try to always use a fresh sharp for every shot. Good luck!