My washing machine is 6 years old. I found what I think is a good deal on a motor (about $50). I was just wondering if it would be a good investment to have a spare motor around.
Motors don't break... the brushes used to power the coils or the golden fingers used to get the power are for sure worn out and need replacing. This can be a difficult task sometimes and these parts could cost $50, so by replacing the motor with an equivalent type you should expect the same life span based on the usage of the machine.
In this picture you can see the brush (inside the yellowish bracket) and the commutator (golden fingers) it touches (here they are dirty - but in good condition) usually they would need to get cleaned on change of brush - but if they are badly worn the motor could be rendered useless as you can see - they are not replaceable on this version.
A nice picture showing the complete design of a coil-motor. The only things that break in here are the brushes/commutator and in rare cases the coils themselves could burn if a high current flows past them. The coils never burn from just running. These motors can run forever as long as they have power to them (even if you physically stop the shaft and put 100% power they won't burn); it just generates strong electromagnetic fields.
According to Murphy and his annoying law, if you buy a motor, then you'll have a solenoid go out, or the controller behind the dial will go out. I've found it's cheaper to wait for something to actually break, if you can't predict which component will break, and then decide if it's worth fixing or you're ready for a replacement.
Not really, over 5 decades of being the appliance repairman for family and friends, I've yet to see a washing machine motor give out.
All the machines I worked on used split-phase motors, not brushed universals. Unless you get a brown-out that burns the windings out, the motor lasts as long as the bearings. Depending on start system, you might have a capacitor, but that's external to the motor.
You have to know the brand and if motor failure is a common problem with the particular make and model you own to know if it might pay off. It's more likely that you'll be selling it for $25 in a yard sale after the washing machine has been replaced.
Transmissions, wigwag solenoids, belts, switches, timers and rusted out tubs seem to be the biggies.