Typically I let anyone work in with me, but if I'm towards the end of an exercise, gotta a buncha weight loaded and I can tell they're gonna strip the entire bar to warm-up I politely let em know I have couple more sets and it's all there's. In that case, I'll finish, strip the weights and help em load what they need. If I've just started I'll work with em from beginning to end....I'm not a prick about it.....just liftin weights.