There are procedures for storing aircraft which become more numerous as the time on the ground lengthens. For a short term grounding, towing the aircraft a short distance to exercise the oleos may be required and as the time increases, jacking the aircraft up to cycle the landing gear at specified intervals is needed. Engine runs, exercising the flight controls and operating the systems comes into play.
The manufacturers have laid down what needs to be done and it becomes more complicated and expensive as time extends.