My original Featherweight sewing machine manual says to lube the motor so I do. It has held up well through 3 owners who have been avid sewers without needing to replace the motor.
So, I'd say to lube it if it is an original motor. If the motor has been replaced at some point, the newer motor may have the self-lubing gears that do not have a lube point. Take a look at your machine and look for the lube points as shown in the manual available online at the Singer website. If you have lube holes, you may want to consider doing an OCCASIONAL lubrication.
Also note: LostN51 - Billy can answer PM's. He is the resident mechanic that restores older vintage machines. I would trust anything he says.