Dental crown with post. How long will it last until I need an implant?

I have front crowns and a few months ago a front one fell off this was a root canal tooth it didn't have a post when I first got it done, I went the dentist and he put in a post and re cemented it back on, I know in the future I will probably need an implant but my question for now is how long would this crown an post last until I would need an implant , I go for a check up every 6 months and a hygienist appointment every 3 months