Bryan, I'm not as regular with my cleaning schedule, but visitors do provide good motivation to pick up. You've just reminded me that my hockey partners are coming over next month, so I guess the next cleaning will be around Labor Day.
In spite of the size of my layout, things don't get "lost" badly enough to re-buy them. Many of the common tools I already have multiples anyway. Sometimes it is a little harder to find things because one of my crew set them somewhere, then I have to search a bit. If it was just me working I would know right where things are. Small price to pay for all the help I've gotten.
The one thing I really need my crew to watch out for is stray metal objects like staples, screws and bits of wire. If any of those lands on the track, it could take a long time to locate them.
Matt has been working on the same project for the last couple months now. I've been leaving his tools and materials out, so he can dig right in when he comes over. I put them away the last time there was company over, but next time, I think I'll just find a box for all of it and set it aside. This project could go on until late October.