The more established a league is, the lower its turnover, because over time you slowly accrue dedicated users. For every dozen new players, you may only have one or two who end up playing for the long term and keep their team. Younger leagues (which includes ALL of the Cust leagues) will consequently have a significant turnover rate. Cust-9 and Cust-10 are the oldest of the cust leagues, so I expect they're probably going to be the two best for player retention.
