We trend toward the longer baths, too.
Our older daughter is five, so if she wants a long bath, I know that she's not harrassing her little sister, and she's more or less out of trouble as long as she's in there! Or, at least the mess is contained.
If the younger one wants a long bath, well, she's okay by herself for a few minutes, but not quite old enough to leave her completely to her bath. That bathroom is cleaner than the rest of the house, since I can clean everything but the tub while she's in there. If she's in the master bath, I can fold laundry or whatever in the bedroom. Her long bath is my catch-up time!
I also like to play with them while they're in the bath sometimes. We blow bubbles, and still use washcloth puppets.
If we're running short on time, they get a bath together, and they get their medicine (during allergy season, anyway - which in Austin, is nearly year-round!) in the tub, and I grab a book and read them their bedtime story while they're still in the tub, too. Lets me skip a couple of pre-bedtime steps later.