Lookit Mister Fancy over here with all these fancy-shmancy flat surfaces just lying around. You think this crowd has any such thing in their shops?
Anyway, obviously each level must be carefully cleaned after each use with a dust-free level cloth and level polish, then protected with level wax, placed into a velvet-lined, calibrated, and humidity-controlled level case, which is then stored in the level drawer in an earthquake-rated Snap-On level cabinet with electronic shock detection and gravitational wave alarms.
Or, just lean the thing against a wall until you either forget where it is and buy another, or trip over the dog and bend it.