You're all but guaranteed to be able to find a few robot vacuums on sale at any given point in the year. When you would want to wait for shopping event like Prime Day or Black Friday, however, is if you're eyeing a flagship model from a big brand like iRobot, Shark, or Roborock. These brands are more likely to showcase a never-before-seen discount on their biggest and baddest vacuums during a major deals event rather than quietly drop prices during a random week.