I have a MIDI I connected to my CNC via a cyclone. Before I had the MIDI I, I had a Bosch GAS50M. Both M class. That vac runs easily 4-5 hour at a time, but typically 2-3 hours, multiple time a day. I had the Bosch for 11 years and changed out the brushes three times. The CNC has a manual and auto switch that control the vacuum table (side channel blower) and dust extraction. And I have left them running for 12 hour by mistake a couple of times. Heats the shop up, together it's 2 kW. And it will cost me 0.50 USD per hour, that is it.
I just installed the MIDI because it has a smaller footprint and has an exhaust that I direct to my garden so that the fine particle are expelled from my shop. I just ordered some replacement brushes because I want to have them in stock when the brushes wear out. I see no reason to replace the entire motor when brushes wear out. Perhaps when you installed your fourth set, or when brushes start to wear out too fast because of worn bearings or worn plates. And the kicker? The brushes are the same, the Festool outperforms the Bosch, but the brushes are identical.