Unless you're playing with zero girl packs, money and energy are not really much of an issue anyway. You will quickly find yourself with millions of dollars in reserve after buying all the girls and all the upgrades. If you have a surplus of girls you'll also always have someone available with full energy.I could be wrong, but the extend option seems like a double edged sword. You make more money, but the girls end up losing more energy. I tend to only use it if I think I will be off buying an upgrade by $100 to $200.
Personally, I like the extend option for continuing a scene I like longer than it would otherwise play. It's also good for ramping up xp for a girl who's doing something that gives xp. If you let the scene end you might get something like Dancing as your next option which wouldn't give any xp unless she was really low in openness. If you just extend a scene she's already gaining xp for, she keeps gaining xp.
I would like to see some sort of option to designate 1 or 2 of the rooms as "VIP rooms" where you only ever get oral, sex, or group options randomly generated. When I get to the point where sex and group policies are unlocked I'd rather not have half of my girls dancing or posing when there are more interesting things they could be doing.