You will effect the chain line each time you remount the cranks by moving it in a small amount. Amount depends on the crank and bottom bracket axle, as well as the torque. You will also wear the threads on the bolts and inside the axle. I suggest using DuPont Krytox on the threads and under the washers.
We travel with an S & S Coupled tandem. We got 20 trips in before the XT cranks became so worn that we could no longer use them. We don't apply lube on the crank axle square tapers but we do use a torque wrench each time to tighten the bolts.