I dont think so ,i'd heard old radio and amp valves were reaching 'new heights'
There is some old ceramic fuses that are going for high prices,these things are now nearly impossible to find
A butchers i used to work in found out when we [ok me ]dropped a mains fuse on the ground breaking it in two,the electricians, the boss phoned to replace it told him 'no chance in hell' of finding 50 yr old fuses and a new box was about his only option
It was luck that i knew a old retired electrician,[a friend of dads] who sourced the replacement ,which still cost £40
Aye- my brother rebuilds old Marshalls, price of valves is high............and I'd agree that the outer glass and the lack of air which it accommodates is a fairly essential bit of them.......