[RKDinOKC]

I have a reminder on my thermostat that tracks the hours the fan is on and displays that the filter needs changed. The default is 1/3 usage or 8 hours per day and 90 days or 720 hours (had to look it up). They look like they need changing. It's about every 3 Months according to the dates I write on the filters when I put them in. Mine has 2 returns with filters each is 12x24x1. They both look the same dirty to me when I change them.

I can set the reminder for up to 2000 hours. The thermostat also has a clean air mode that lets me set times other than when the heat/ac is running to run just the fan. The defualt is twice as much.