They don't need to be replaced unless there is a problem with them. Most people don't exchange them out ever. There is a rumor that you have to switch them out every 10 years but that isn't true - it probably started because there is a 10 year warranty on the implants but that doesn't mean anything happens to them after that!
That honestly varies person to person but I would say 10-20 years but you would need to talk to your plastic surgeon.
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