Well, a/c do have to have checks performed at certain milestones (i.e. a 500 hour check). But an aircraft is made to fly and it doesn't make any money sitting on the ground. It is up the the MX planners and schedulers to plan which flights an a/c will do to comply with the checks that get perfomed...and obviously to stagger the a/c in the fleet so they all don't have to go in at once.
"If you do not learn from history, you are doomed to repeat it"