I used to have my games (EM) on 5-ball until I started to feel like they were to easy to beat. I like to play them as they were intended, to me, a free game should mean something- so if I start playing for free I switch the game to 3-ball, if I still play for free I will move the outlanes to conservative, if thats not enough I will work on mechanisms to get the ball speed to its absolute max and raise the game.
I want it to mean something when you roll the score over on a game and walk away with 3 credits-
I also actually hate long games, I very much enjoy running down and playing for 5 minutes if thats what I have, I would much rather play 3 games and get my ass kicked than sit there and crush a game for 5 minutes and have to turn it off mid-game because i need to get going. I like hard games, it forces me to learn how to play better.
I don't worry about the kids, we have a big bowl of quarters, they can stack it up and play all day- they don't care about the score, just the lights and sounds.