I take mine on and off, maybe 3x a year so not much. My theory from general mechanical knowledge is you have a higher risk of damaging your threads from:
1. The screw working itself loose and moving around gradually damaging the threads
2. Over tightening
To prevent 1 people often use 2. Use a threadlocker to reduce the risk of both of those greatly and can fill in some voids and reduce vibration and movement. Racks put very little force outwards on a screw, the screw is just "there" to provide something to suspend the eyelets from falling. The tightness required is only to prevent the screw from vibrating and falling out which threadlocker does. A $5 tube can last you years if it doesn't leak out first.

Also, use the softest screw available (aluminum?). Allow any potential damage to happen to the screw instead of the boss.