No serious dentist would replace original teeth with implants if he still sees a chance of saving the original. Implantation is always their very last resort. Also, having implants doesn’t mean you can live a careless life „until you’re dead“. To not loose them too, it’s even more important to maintain a proper oral hygiene. If your jawbone-structure starts to degrade, you rather end up slurping your dinner through a sippy cup for the rest of your life.