Gary; you can hook up a portable tank at the end of the run, assuming it's permanently plumbed through the workshop. This would increase your reserve air substantially, but the compressor still can only supply what it can supply, so it ends up running less often but for longer each cycle. There is no simple solution that's cheap.
On the pneumatic ROS issue, they're a hellovalot less expensive than a decent electric sander, and waaaay faster and lighter! I think mine is 10K RPM at full throttle. Also, less that can go wrong mechanically.
But yeh, you will have the compressor coming on in the background.