score:6
Depends on your status and ticket type(s). Access rules are fairly complicated: See https://www.lufthansa.com/us/en/Lounge-types-and-access
In "most" cases (business class ticket and/or Star Alliance Gold), you will need a same day departure boarding pass to access the lounge. So if you already have a boarding pass for your connecting flight when you arrive, or if you can check in right away, you can access the lounge (provided you have proper access credentials in the first place).
You can enter and leave any qualifying lounge in the airport as often as you like. "Lounge hopping" can be fun, if you have a long layover and are stuck at the airport.