Overall I see decent retention.
Thing is, if a player consistently loses the casino becomes “unlucky” to him and he moves on. Many players are very superstitious. In this case the casino group with several casinos that can crossmarket has an advantage.
It’s kind of funny, players often complain about rigged casinos. Meaning they are set for a player to only lose. This would make no sense for the casino, rigging the software to have more regular wins would be more profitable.
Also, the way you entice the player in the first place makes a difference, as well as how well the casino pursues the original path. If you entice players with bonuses, the casino hopefully offers them continuously to bring the player back.
If you entice them with new games, hopefully the software people keep putting these out.
So, retention needs to be in step with promotion to support the type player they attracted.
There are many aspects to this, and I am sure I only know a portion of them.
One thing I do know though: if the player comes back to you to find another casino to try his luck with, you win.