As my two Collins S-Line stations received tremendous amounts of TLC at the hands of Chuck W9KR, the vacuum tubes were checked with any out of specification replaced.
I am planning to buy at least one complete backup set as reserves.
Tubes are not “forever” items, and a ham would not even have a chance of a quick repair if you didn’t have spares on hand.
One of decisions is to what depth should I put in spares? Would one comprehensive set between the two stations be sufficient? Or one comeplete set PER station? Or greater depth of all or perhaps just certain tubes?
Be careful about how your suppliers ship your tubes. One box ordered looked like it was place-kicked at the USPS perhaps in an afterhours soccer match! Amazingly the tubes all survived and tested okay.
I am looking for advice on storing spare tubes, especially as some become rather rare and expensive. Any time-proven methods?
73
Steve
K9ZW
With Varying Frequency - Amateur Radio Ponderings 
In my experience tubes in radios that are only used occasionally will last a lifetime. As an example, I built a Heathkit SB-101 transceiver in 1967 and it still has the original tubes in it. Also have a Hammarlund HQ-170 and many old radios with original tubes. Granted they only get little use now however the tubes are fine. The enemy of old radios is paper caps which get leaky and old carbon resistors that drift up in value.