Does heat kill tubes?

My system went into a steel container for the past three months while my house was going through remodeling. Container sat on my drive way which receive lots of sun, interior temperature often reached 120+ on hot days. My SF Line 3SE was working flawlessly before packing into the box, it now has a noisy channel which was caused by a bad tube in the buffer section.

Tubes are not as rugged as transistor, but they should be able to withstand 120 degree easily without operation. I assumed if it could survive years of life on the shelf, it should survive a few months in a container. Or am I wrong?
I think you are right. I'd consider transportation into and from the container, new setting up and all that moving around being the cause of that failure. A tube guru once told me: "tubes last much much longer than you would expect - as long as you are nice to them." Being stuck in a hot container can't be nice? :-)
Good luck!
As far as heat is concerned, tubes can take a lot more than transistors. Since the tubes get that hot or hotter in normal operation, I don't see how heating them up would damage them.

I think the tube failure after storage in the heat was coincidence.
120+ is literally nothing to tubes even 180.
did you or anyone else accidentally hit the box with your car or truck?:-)
Not operating can be hard on tubes because gas (that leaks through the glass) can accumulate. High temperature may speed up the gas accumulation. Operation of the tube cleans out gas.

However 3 months is not that long, and 120 degrees is not that hot, so I would bet that your tube failure was just a coincidence.
As I ran my pre amp a little longer, the noisy tube seems to cure itself and noise is gone!

I know tube can handle very high temperature, so 120 should not be an issue. My wife did drop the box from about 6" height, but units were packed in boxes with all packaging materials and 6" is nothing comparing to what UPS can do. As for solid state, I can tell you semiconductor is processed at very high temperature in many steps (900+ C) and operates in 140+ F without cooling normally. I know because I am a process engineer in AMD.

So should I change the once noisy tube or just keep using it?
Sounds like the gas getter got the gas!