I always wonder why people apply bog standard job rules to something like being in hololive. It's such a unique position and strange unusual job, this "stay at one place for a few years then move on" mentality doesn't apply at all imo.
Plus for many girls landing the golden holo ticket is literally their dream come true, it's not just a random step on the ladder.
There is no reason at all why holos wouldn't be able to do their job for 10 years or more if they wanted to.