Originally Posted by
reddog3
It depends on the type of bottom bracket in use. If it's a square taper cartridge BB it's not necessary. Outboard bearing styles require require square shell facing for longevity. If you have the outboard bearing style and you've had the bike for a couple years with no bearing problems, it's a good indicator of a BB shell that is good to go. Needs only to be faced square once. There's nothing to cause that surface to wear.
It does not depend... the bb shell needs to be faced so the cups, cartridge, or external bb sits flush against the shell although you are right in that external bottom brackets are intolerant of less than perfect frame prep.
It is a simple job to do if you have the right tools although it can also be done very carefully by hand although you should have bottom bracket taps to chase the threads and these are not cheap.