Keeping the original batteries in your games at this point is asking for trouble anyway, of the games that I've been opening up and inspecting/cleaning/whatever and featured a save function I would say 25% of them had leaking or corroded batteries. Leave something like that in there long enough and the acid contaminates the rest of the circuit board, with migrating corrosion.

In five or ten more years people won't be asking if the original battery is intact, (assuming this was ever an issue,) they'll be asking if the game still saves and more importantly, if it still works at all.