Implants don’t have to be replace every 20 years, it’s guideline too replace them at some stage, but there’s plenty of people with older less tested implants from decades ago, and they have them in. My auntie had breast cancer in 1994 and still has the same implant and as it still looks brill, won’t be changing it in the near future.
Most girls tend to change them sooner for cosmetic reasons, like sagging, but there is nothing to say you have too.
Like everything has a guideline on usage, no-one really sticks to them, who actually changes their toothbrush every twelve weeks? Mine is twice a year on a good year (lol!) despite using it daily xx