Bring different sizes and don't let a guy use a large size condom if he's too small. Guys will do that, it's a weird mental thing to make them feel bigger in their head. Most guys stop themselves after they bust but some (me personally) can and do keep going for awhile after. The only problem with that, especially with older guys is they obviously start to get soft and slide out. And the messed up part about that is some guys will be embarrassed and not say anything