I would say do the following:
- Leave the Amiga at a place where temperatur doesn't change much if you don't use it. Better keep it in a room than put it in the cellar or loft.
- Clean off dust after you haven't used it for a long time.
- Don't touch any ports with your fingers.
- Remove old batteries from things like memoryexpansions before they start leaking.
- Buy some small cooling metals and put one on every chip, using temperature-conductive paste ( shit I don't know what that's called in English language )
- Don't put physicaly damaged disks or disks which have been spoiled with liquids into the drive, because they might make the heads dirty or even damage them.
- Also reseat socketed chips from time to time because with heat extraction and contraction they slowly work themselves out of their sockets and afterwards a small electrical flash could kill them if they are not socketed properly.
Ok, I think that's all which came to my mind, although I for myself don't do any maintainance on my A-500. I just use it about every week and when it dies I replace the dead chips - no problem as long as there are enough Amigas around
And if a drive failes then in most cases it is just not adjusted properly, which I can usually fix.