when do Broadway musicals get updated?

Wednesday, June 9th, 2010 at 1:19 am

well i seen the musical CATS onstage and on dvd and on the dvd they had clips from the first time cats was on stage and it look much better now that it did back then they got better costumes and a better looking stage so when do broadway musicals get updated and how do we know and i am not saying when do broadway musicals get revival