Every 2-3 months is fine for robot vacuum filters.

Unless you have heavy pet hair or serious allergies, replacing every two or three months keeps performance strong. The manual might say monthly, but that’s mostly to cover their liability.

Filters get slower over time, not dramatically worse all at once. You’ll notice the vacuum sounds different or the bin fills faster when it’s time. If it’s washable, rinse and dry it in between—that stretches the life.

For most people, the difference between a fresh filter and a three-month-old one is tiny. Save your money for bags or brushes instead.