Hmm, interesting one.
I would say it depends on the material.
Cast parts, happy to leave outside
Larger assemblies such as axles, springs, gearboxes I would steam clean/hot pressure wash, give them a spray of clean gear oil/chain oil and bung them in the corner of a dry ventilated shed or clean and spray with a 3:2 waxoyl:gearoil mix and keep them outside on gravel with a tarp over them (not tied tightly/sealed and bung vent holes/air intakes etc)
Tinwork, now, depends on its condition. If generally good I would clean and store in a dry shed. If grotty, I would clean off rust as far as possible, give it a soaking/spray with light machine oil and store inside.
If rare/valuable, get it cleaned, remove oxides, sandblast even, prime it (or lacquer it in the case of alloy castings) and topcoat it (dosen't matter if its not the right colour, at least it is protected) and squirrel it away in the rafters until the day you die
I try to clean, oil and store in a dry location wherever possible. Under a tarpaulin hoosie if not possible, although this risks condensation.
My tuppenceworth anyway.............:cool2:
Alec.