I keep my bikes in my cellar. It would normally be really damp, but I use a dehumidifier. It works great for keeping the cellar dry but it's awful for 25+ year old tyres, especially tyres with tanwalls. It doesn't take long for them to dry out and go all crumbly.
For this reason, I usually...
Quebulas' 1989 Peugeot Anaconda
I've never entered a bike into the BotM so, here's my entry.
https://www.retrobike.co.uk/threads/peugeot-anaconda.471291/
Is the seatpost steel? I bought an 89 Kili and it has a steel one fitted. It is stamped Shimano but no series numbers are on it. The steel is incredibly thin. I just imagined XT seatposts being aluminium.