Ask the Little Bald Bastard

I'm kitty-sitting.
  The Barrymore is about one and a half, and Charlatan is around a half, so neither of them are kittens in that "Look, she fits my shoe! And in that saucer! And in the fold-up couch! Hey, where'd the kitten go?" sort of way. Still, they are young enough that they get pretty rambunctious. Putting a paper bag on the floor is a quick way of sentencing it to death, and anything that rattles or rolls on the floor will get batted around until it gets stuck under the couch.
  It's all hunting, really. They get some exercise, and it's much better than stumbling over headless rodents they've deposited on our doorstep. Still, it sometimes gets a bit scary when they run out of toys. If there's nothing worth batting about, they'll start harrassing each other. I've been assured by two sets of experienced cat-owning parents and someone at our vet's office that this is natural. The consensus seems to be that, as long as they aren't actually clawing each other, then they're just playing a little rough, and it's fine. Still, I can't help but be concerned when they're wrapped around each other, hissing or yowling like they're trying to kill each other. So I find myself compelled to drop whatever I'm doing and go distract them when they start to get too hostile.
  I do mean whatever I'm doing. Eating, web-surfing, sleeping. I'm supposed to go to the grocery store while Amy's at work, and I've been reluctant to leave them alone. They are certainly as cute as drastically mismatched buttons, but I won't be disappointed when they're old enough to be as lazy as I am.