when to pull the plug??

I say pull all the stuff off the tank and use the tank for a smoker/bbq pit. If you got 11 years out of a oil less compressor you did pretty good. Save/ borrow and go buy you a upright 60/80 gallon with at least a 5-7 hp motor and never look back. You will spend pretty close to a grand, but it will do everything and faster that a home mechanic could and should ever do. Just my 2 cents. Plus with a little metal and a weekend of work you will have a good brisket smoker to feast out of after you finish working it the shop all day.