I went through about 2,000 shots before i replaced my first rubber. At the time i was using way to much silicon oil to lube my gun which caused it to swell up. I bought 3 (1 to use plus 2 for replacement) after that happened and i have yet to use my replacements.
As long as you don't over lube the gun i don't see you needing a hop up replacement in a long time. The stock (plastic) rocket valve lasted about 2 weeks before it gave out in my G19, so you'll have other parts break before the hop up.