Quoted from PinRetail:The better answer is to convert all your pinballs to NVRAM as soon as you can.
I second this. Absolutely convert to NVRAM. In your one or two games that needs batteries due to things like Midnight Madness, or the TZ clock, use a remote battery holder in a baggie in the bottom of the head.
It isn't just for peace of mind. You are just a steward of the games you own. The more durable they are, the better.