While I was training to be a machinist in the Navy the instructors stressed not to be any more accurate than what the print called for. They said you'd be wasting time.
Is it okay to not sand the surfaces of a piece that will never be seen to the same finish as the surfaces that will be seen or would it be shoddy work? You know the back of a cabinet, bottom or back edge of a shelf etc. Am I burning up sand paper and time making all surfaces seen or unseen the same finish?