I see pros and cons to this. I would propose sudden death at the end as we see in some existing games rather than say, okay, 15 minutes are up, you are done.

For tournament play I do like fast timed games. Not something where it takes 30 minutes to get through ball 1.

I could see adding a simple flipper code while in attract mode could trigger a couple different options. For a party mode you could do as follows, and even have the times be adjustable in menu.

1 ball game
Immediate multiball upon game start something similar to midnight madness.
I would max 3 balls. Some games that empty their troughs can get excessive and can't really make shots.
Ball saver is on for X number of minutes.
When you are down to your last ball maybe get rewards with 2 and 3 way combos etc as commanded by a single lit shot.