Sadly, there are a lot of parts that you need to regularly replace. You must replace the filters every two months and eufy sells packs of six sets of both the foam filter and the high-performance filter. The side brushes and brushroll guard must be replaced every three to six months, or when they’re visibly worn. You must change the brushroll every 6-12 months, and eufy sells these replacement parts through their website or on their Amazon store.
Note that the manual we received with the 11S was Version 1 and didn’t include the replacement time for the brushroll guard. The updated manual, Version 2, is available online and includes the replacement time for the brushroll guard.