personally I would not use humidipacks inside of the mason jar...... my approached is based on cigar storage, which just happens to be in that 62 to 65% RH range.
Once your jars have reached your desired % RH, then store those jars in a plastic food cooler with a passive or active humidity device to control the RH of the environment external to the jars.
If the contents of the jars are at 62% and the external environment of the jars is maintained at the same 62% RH, then they will never drop below that 62% RH
IMHO..... it's less effort to control one environment than several jars...in the cigar world they refer to this as a food cooler humidor as a "coolidor" (a poor man's humidor)