Back in the day of speed glue, people used to take their rubbers off and re-glue pretty much every time they played. These days, people who boost, when the boost wears out, in about 3-5 weeks, will often take the rubbers off, re-boost and then re-glue. Every so often I will slam the edge of my racket, take the rubbers off, fix the edge of the racket, boost the rubber, and re-glue. But, if there is no real reason to take the rubbers off, and you are just gluing with the standard Water Based glue that the ITTF wants people to use on their rackets, then there is no real reason to re-glue.
Right now, my rubbers have been on without me messing with them for a few months.