What is the life expectancy of a washing machine motor?
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.