Hiya buttons, the skin and flesh around the implant will sag, yes. Implants placed under the muscle have better support and will potentially sag less but don’t forget, muscle deteriorates, especially as you get older. We don’t last forever honey!
If you still have implants in at 60 your boobs will probably have sagged the same as anyone that age, don’t forget at the moment the advice is to get them changed every 10-15 years!
The only reason they say about getting them done every 10-20 years is if you want to try and upkeep with the ‘perfect’ look. Sooner or later age is gonna bite u in the ass! Better just to go with it xx