No matter how new your batteries are, they can leak and eat your very expensive circuit boards.
You can install remote battery packs, coin cell batteries or other devices to prevent board damage, but the ultimate solution is just replacing the regular RAM with NVRAM. No batteries to replace yearly, no losing your high scores, no leakage, and your data is good for 30 years.
Andrew "Barakandl" here on pinside, sells RAMTRON FM1608 NVRAM chips that eliminate the need for batteries.
They cost (depending on how many you buy) $8-12 USD. This makes for a VERY affordable solution.
There was some argument on the forums saying that the FM1608 was not going to work on pinball boards because of some kind of "compatibility issue", although when I looked up the specs, they seemed to be a perfect match.
So I got some chips and set off to put them to the test.