There are a good few young drivers with F1 potential - Leclerc, Norris, Rowland, Newgarden, Schumacher, Gunther, Aitken, Russell, Matsushita etc. Start using them as new drivers and maybe allow us to suggest in PM who we'd like to have as time goes on so you can then add them to the rookies list.
Current drivers can go on for ages, look at Verstappen, Ocon and Stroll - they have the potential to race until the 2030s