I’ve changed mine once after 4 years of moderate use in a quite well insulated 1700 sqft apartment with wood floors, no carpets but a decent amount of visitors and occasional tiny dog.
Those filters were used though, no idea for how long (they only had like 70 hours on them according to the onboard tracking, but that would be easy to manipulate even by accident)
IQair recommends a yearly replacement for my HEPA filter, but my environment had a fairly low amount of particulates to begin with (new building with filtered air intakes) and workload split between multiple units.
