Alkalines slowly drain over time, even if they aren't hooked to anything. Lithiums do this at a much slower rate, in addition to the higher mah rating per battery, which is why they have 10 year expiration dates to them.

Biggest advantage of all....... lithiums don't puke like alkalines do. You could theoretically run for a decade or more on a set of batteries.

-Hans

Lithiums technically CAN leak, but they are generally constructed better to prevent it and it occurs far less often. As long as it vents any internal pressure, a lithium shouldn't leak. Here's a good explanation of how the leaks actually occur.....

http://knol.google.com/k/everything-you-need-to-know-about-primary-battery-leakage#

The batteries are there only to maintain the settings and scores, but you do need them in place to get the machine to boot, and it normally won't boot without a good battery.

There's a lot of options out there too, so don't think that you have to go with any particular one. Remote packs for alkalines are good, swapping to lithiums is good, chips are available that allow you to run NO batteries in some machines. Some guys even run certain capacitors that do the same job, as long as you have the machine on for at least a hour per month. I've personally switched both of my machines over to take 2032 lithium coin cells, but am considering going with non-volatile RAM and just eliminating all the batteries completely.

The only thing you really need to be concerned with is that the blocking diodes are in good shape, as lithiums can pop if you try to charge them up. Then again, alkalines do the same thing too. Lithiums also react badly if you soak them in liquid water for long enough, but I've yet to see a pinball machine that you would want wet circuit boards on.

There's no need to do the annual swap with lithiums either. The reason you do that with alkalines is because they leak when discharged too far, but a totally discharged lithium becomes inert and won't leak in that situation. Heck, lithiums become SO inert when they're dead that the EPA actually allows dead disposable lithiums to be thrown out in the trash.

-Hans