I try and keep mine fairly clean. I find it helps me think more clearly if my workspace is somewhat organized and free of a bunch of crap I'm not currently using. If I put a solid 8 hours in the shop on a day, I probably do a few mini cleans every few hours depending on the mess I'm making. Now that my cars are all together and drivable it's much cleaner. I also have the luxury of having the shop attached to a huge barn with upstairs storage, so if it starts to get out of hand I can put some stuff upstairs in my "parts dept."