Care and feeding of all tape machines.

This question will probably be a blast from the past, but I own a Tascam 424MKII 4 track and I was wondering what kind of regular maintenance I should be doing on it (aside from head demagnetizing and head and capstan roller cleaning) to keep it in good shape and extend its life.

You've basically touched on the two main things. Keep the transport clean and demagnetized. This is true of all tape machines, though the methods for achieving this will differ greatly. Otherwise it's just a good idea to keep the rest of it clean. Keep any debris (tape always sheds and leaves debris in the transport) cleaned out and keep dust off of it. I recommend keeping it covered when not in use. The dust you keep out will also help the faders and pots last longer. Unplug it when it will not be used for a while. When it is plugged in you are safer if you have spike protection and/or some kind of regulator to insure it is getting good power.

That and a good dose of common sense about does it.