museum
Lots of hardline opinions, so my 2c:
If the machine cannot (or should not) be used, then preserve and donate to museum.
My machines are daily drivers, so they're a "converted" / upgraded. (My "collection" of retro / vintage daily drivers is basically every facet of life, from fridge to lawn mower to vacuuming.)
A word on collectors: You have a passion. It inspires. Can't beat the looks of your machines.
Then I see collectors entire estates on auction sites. Whole collections in prestine condition entirely for sale.
Why do these collectors eventually auction their entire "museum"? Hmmm... well I don't want to be in a position of inevitably parting with a passion that eventually must go ... and to whom?
I still 'luv the looks of a preserved machine! Prestine is just not my goal. Everyone's different.