Yeah, as a strategy for a particular campaign it requires the characters to be in synch. You could add new ones mid-campaign, but they'd be younger than the original group. It does probably work best if the group are either serving together or are remaining in the same subsector, but depending on the career mix and player availability, they might roam further and come together when one of them needs help or finds something interesting.
There's no actual need to take things to mustering out, really. Just play the group through their careers and let the term events influence how that term's adventures play out. Maybe run roughly one adventure per chronological year? Don't use the training rules for advancement, just have the advances granted by various things in the term give those after they are resolved, or at the end of term if appropriate.
It could also be a way to do a planet of the week style campaign without having to track all the tedious jump travel. This session we're on Efate, throwing Jaxon a surprise birthday party, which does not go as planned... next session, 8 months later, the gang meet up by chance at Lanth. A year later, Monny finds themselves in big trouble on Rhylanor and sends out a call for help. The two other players available to play are the ones whose characters are close enough to respond in time. The next time they find themselves gathered is back home for Jaxon and Monny's wedding.