Hi again Teena,
I always put a dab of grease on the shaft, at the end where the grease tube is at. The tubes always seem to be blocked, so I don't rely on them and the Singer grease tubes are always full of holes. I'd put about a rice grain bit on these two areas. If there's no grease the motor will suffer (in theory) but since the motor manuals always say to grease every six months and nobody seems to have ever in the history of Sewing machines done this, and they're all still working.... I do it anyway.
I'm not quite 50 yet, but most of my friends give me strange looks when they hear what I do in my spare time (repairing sewing machines, not the serial killer thing
)