I run 7.2" vac motors and a recommended brush change @ 300 hours which is about 1 years use for me. I tend to play safe and change them at somewhere around 250. Ditto for my pump.
The 5.7" vac motor brushes tend to have a greater service life, and it's been suggested to me as high as 600 hours. But a check at 300/1 year would be wise. Considering the cost of the brushes, it would be wise to change them at the time anyway. If you have access to a 110 volt transformer, it is beneficial to power your machine from this and run the brushes in for half an hour at the lower rpm 110 volts will give you. Ditto the pump too.
Safe and happy cleaning
Ken
