If you have to heat a bolt to remove it you should replace it.It's a friggin' bolt,I think the security of knowing that it's good is more than worth a few dollars for the bolt.
When I replaced my rear brakes I sprayed it with lots of PB smacked it a few times with a hammer,and being as I didn't have the approriate torx,used the vice grips to get it out.
Just a word of caution,when the bolt breaks loose be careful not to cut yourself on the splash shield behind the rotor.It hurts BAD.