I always try but never succeed in not disconnecting my brake cables from teh calipers. It just ends up being necessary. If when you put it all back together you need a little more inner cable length, you can shorten the outer cable a little. It depends on your outer cable routing, if the curves are as smooth and loose as they should be. If you have a big cable length problem, you will just need new inner cables. Probably the outers won't need replacing.

Don't trim the brake cable ends too short at the calipers.