You can read on the RAM installed - "timekeeper ram, contains lithium cell".

Leave the batteries out - in fact, you probably should put a note inside the holder "DO NOT FIT BATTERIES".

These types of battery backed RAM have a shelf life of around 10 years, about the same as lithium batteries, so when the battery inside starts to fail you will need to replace the RAM at that time because it's all built into one package (not the smartest idea). You will also need to do something about the battery backup then.

Until then, I would leave it and enjoy the game.