Two examples I'm working with. 1) 2001 Escort not used since 2017. A/C not working and gauges show zero pressure. Did the 15 minutes on a vacuum pump followed by 15 minutes rest. Vacuum held steady so no obvious leaks. Assume seals just shrunk from inactivity and will be ok after some use. 2) 1988 motorhome not used since 2011. Never imagined the A/C would work after sitting that long, but a few days ago I hit the A/C button and the compressor engaged, noisily for a little bit, but the air blew cold. Far as I can tell it's still on R12. Do these old systems hold a charge better?