Rust and peeling paint are a turn off. If display items look shabby, people may expect the rest of the operation to be sub standard as well. That's definitely not the case with the C&TS but why risk turning people off? Paint is cheap and easily applied. The rest of a cosmetic restoration is probably less important for the general public but I think it's a good idea, none the less.
Too far away in Michigan to help but two of us painted the display 2-8-0 (ex Potosi Y Rio Verde #4) at the Huckleberry so I know it can be done with a small crew in a day.
Michael Allen