implant replacement

For those of you with the implant, when did you get it replaced? I've heard you need to get it replaced at least a month before it runs out but I don't think I'm going to be able to do that! My GP doesn't do implants and the sexual health clinic in town can't book me a consultantion until the 7th Nov, and the date on it is 14/11/2016 so that cuts it really fine. They said I could go to the walk in clinic next week but there's no guarantee so I could sit there for two hours for nothing. Am I stressing for nothing??