I had a badly tweaked custom frame chased once by a frame builder years ago who straightened the frame and I think he added only $25 for the BB chasing which he said probably was not needed as the custom builder would have done it and I had no reason to doubt condition and the threads were good. If you are moving to outboard bearings and saw lots of paint or other reason maybe but unless your heading out on a tour a shortened bearing life might not be a big deal and could then have it done.