[Bavarian05]

Originally Posted by RLF

In his book, "Get Better Sound, Jim Smith recommends having a second set of tubes on hand for a particular component and swap the old ones out with the new ones every so often to see it the sound improves enough to leave them in. If the new ones sound better then its time to change tubes. If not, reinstall the old tubes and repeat the process again in several months. He states that tube deterioration can be fairly substantial only after six months even though the manufacturer gives a longer tube life expectancy.

Don't plan on swapping your wife though

Good advice! :-)