Are you using the built-in automatic sensor cleaning function in the menus? As I said, with that enabled, I haven't had to clean a sensor in years. Even with my old 10D, and the supposed "dust magnet" push-pull 100-400, I only cleaned it once a year.
I'd suggest you take a specific shot before cleaning - f/22 (or whatever the minimum is), manual/out of focus, of the blue sky - to see the sensor issues right before and right after cleaning next time, to be sure it's cleaned. It's hard to believe it's accumulating that quickly. Even the 70D, which doesn't have the automatic on/off cleaning, iirc, shouldn't get dirty that often.
Do you try manually cleaning it just with air? I have a Rocket Blower to use with the Sensor Cleaning function that just flips up the mirror so you can blow away the dust. Doing that regularly, I only had to actually swab my 10D sensor 2-3 times, ever. That was a process I don't recommend and Im glad those days are past for me.
http://support-th.canon-asia.com/con...202789800.html
http://support-th.canon-asia.com/con...202789400.html
I'm pretty active on DPR and haven't heard sensor dust issues in years, so I don't think it's an inherent 80D problem. Searching, this is about the only discussion I can find in the whole 7D/x0D family -
https://www.dpreview.com/forums/post/59109822