i dont think it will affect the estimate, but it will probably affect the work. in that you will have to get it done faster in order to get the next guys in there. however, i have never had to hurry more than my usual pace. but you had better, at the very least, pre order all your material and have it on hand, if it is something other than lights, that can be added anytime they get there. that is, they are not going to get covered up by say, sprayed-on insulation or fireproofing or something like that.