Nowadays Power Rangers teams last for two years so you would need to update it fairly regularly but the formula really doesn't, so you really wouldn't have to change much, every two years the new casts films their little bit and records some voice-over, and when the new era starts you close the show for a few weeks to add to the pre-show museum and get the stunt-team comfortable in the new costumes, and then reopen as a 'New' Attraction.