The trouble with a high turnover of younger servicemen is that it is murderously expensive. The length of training vs return becomes disproportionate, the balance of those in training or instructing vs productive degrades FE@R or requires a manning uplift.
When it comes to aircrew you have to factor in more training aircraft and more OCU aircraft too. We already have fleets that cannot train enough quickly enough to cover their normal loss rate (eg Sentry), so these fleets would simply cease to exist.
The old and bold are cheap and are partially self-funding as they are not drawing their pension or EDP. Sadly a lot of fleets are already diluted and struggle to fill the traditional supervisor and instructional posts.