I've removed and reinstalled subframe bolts before and I've never had a problem. You should definitely torque them, but I wouldn't go as tight as the spec for a brand new bolt. If the book says to torque them to a certain value and then go X number of degrees, it is because the bolts are torque-to-yield and you're putting a stretch on each bolt. If it was a head bolt, yes I would change it without a question. But, since it's a subframe bolt it doesn't experience the same repeated pounding and torque is not as critical. If it's going to fail, one bolt will break at a time. It's not likely that's going to happen until you whack a curb really hard. If it were mine, I'd torque them and inspect them at each oil change when you're under the car. Since you're the driver of this car (are you?), you're going to notice a change in alignment if a bolt breaks and the subframe shifts because it will change the caster of one wheel and pull to one side.

If you're at all concerned, just go pick up some new bolts and forget about it.

Steve