DFC, your answer is fine for a basic TXPDR.
However, modern TXPDRs in up-to-date aircraft are rather more sophisticated than that, and switch themselves to standby immediately one of the selector controls is moved, and remains in standby for a second or two (I forget exactly how long) thereafter.
Furthermore, leaving it at ALT/RA/TA setting (depending upon aircraft type) leaves the TCAS system operative and monitoring other aircraft. If you select SBY you lose that protection. Not a good idea.