How often should I replace a robot vacuum brush?

Main brushes typically last six to twelve months of daily use, side brushes rather less — and both degrade gradually enough that most people leave them far too long.

A worn main brush stops reaching into the floor, so pickup falls without anything obviously breaking. Side brushes bend outwards permanently and start flicking debris away from the machine rather than into it.

Hair is the accelerator. In a house with long hair or a dog, expect to be cutting tangles out weekly and replacing brushes at the short end of the range. Rubber or anti-tangle rollers help considerably.

Order by the exact model number printed under the machine, not by the range name — makers reuse range names across generations with different parts.