Without tabulating the data, my gut feeling is that the biggest turnover is in the fall. As the seasons end (different dates by level), some players are released and many others depart via minor league free agency following the end of the World Series.
The Roster Matrix would provide the precise answers over time if anyone who wants to mine the data transaction by transaction. They go back many years.
Having said that, there is no guarantee that the history under Mo and Gary LaRocque is the same as the current regime under Chaim Bloom/Rob Cerfolio/Larry Day. It should be interesting to watch.