Yeah, it's amazing what happens to those cushions. I think that oil contributes to the "goo" stage.
That Ismacs site is amazing. The number of manuals they've managed to collect and archive in one place is such an incredible contribution to the sewing community. Interestingly, there are a couple of different versions of the 221 manual. Some have more detail than others about maintenance, so download all that you can find and compare them. You can learn a ton from them.
I've done that.
I make sure now that my laptops go into sleep mode when the battery is close to dead. You can find that in Control Panel - Power Options.