I have had frames over the years that were refinished numerous times, and each time had the bottom bracket shell refaced. Once you do that a few times, you need a spacer to get the chainline right. Tom Kellogg (Spectrum) once told me he thought it was a waste to reface every time you refinished a frame - chasing the threads, and if necessary cleaning the paint of the outer lip of the bb shell, was just fine.
Duncan Granger
getting ready to go for a COLD ride in
York, PA (where I work)