Quoted from PinballManiac40:
Here is the way I put it to people when I work on their games. Say, I install Lithium batteries now in a game for you instead of NVRAM. Somewhere down the line, you sell the game and the new owner reads on the internet that you need to change alkaline batteries every year. Some people may not realize Lithium batteries last much longer and should not leak. Very likely what will happen is that the new owner (most likely, new to pinball ownership) will install alkaline batteries because they are cheap. So now the game is at risk yet again.
So, I suggest that anyone who does install Lithium batteries in a game, put a label over the batteries stating "Only replace with Lithium batteries". That way the MPU board will be protected for a much longer life. New replacement boards may not be easy to find in 10+years.
Does it matter though if they are in a remote battery holder?