The main thing to remember with VF2 in particular is that it lasts a long time! People who expect to finish a game in a day or so needn't apply!

The game is designed so that it will take six weeks or so to reach the sort of position where all the items are unlocked and available. That way interest is spread out over the period; each generation brings new upgrades to install and prices are set so that the most expensive upgrades come at the end. That way younger and/or less wise players won't be tempted to spend all their money on something they can't really afford.

I'm not saying players need to spend a lot of time over those six weeks. You only really need to check on your peeps two or three times a day, for five to ten minutes a time. Just make sure they've got enough food, are not sick, buy them the occasional upgrade, see if they are willing to try for another baby perhaps, look around for some collectibles and so on. That's why VF is called a casual game.