I reduced the default maxpos from 100 to 60, and raised the threshold for the pid (set temperature) to 16 K (from 15 K). Since our 4K JT is sitting around 30% right now, this means if the manifold inlet temperature falls below 16 K, the JT's MaxPos will start to drop at the rate of 2%/minute from 60% to 30% before it actually starts to close the valve. That's a 15 minute buffer. After that it will start closing the valve as MaxPos continues to fall, until the T_mi rises above 16K again.
At that point MaxPos will crawl back to 60% at 2%/minute, but the actual JT position will stay wherever it was. The TO will have to raise it by hand back to where it was.