Never had the dust, but we are pretty diligent in cleaning it. Evap and condensor coils twice a year, filter once a week. Even when we didn't full time, changed filter every trip or every other. We buy the filter material in bigger sheets and I cut 20+ filters at a time. Cheap insurance, doesn't cost hardly anything, and definitely makes the coil cleaning easier. Last thing you want to skimp on is a $500-$1000 AC.
I'm not sure what the white dust is you're experiencing.
John and Rebecca Dickson
Emma-8 / Little John-5 / Iva-1+
2013 Ford F-350 Lariat FX4, CC LB PSD, DRW
2015 Jayco Jay Flight 28BHBE (#8)