I know I've had mine for something like six months now, and it's the only grinder I've used daily since I acquired it (except for two or three times in that time period that I've used my MFLB Finishing Grinder because I pulled out my faithful ol' MFLB for a spin)....and all I've ever done is brush it out immediately after every grind with a dry brush (and every few grinds, I scrape around the rim edges with a fingernail, or simply rub off the residue there with a fingertip...or a combination of both).
It's not perfectly clean now, of course. But I still think it's better than any other grinder I've had, except maybe the SLX 2.0...but the SLX feels like sandpaper when grinding, even when it's completely clean. So my SLX feels a bit gunked up even when it's clean.
Here is a pic of my BCG that I just took a few minutes ago. I mean, there is of course a bit of residue built up, but I feel that it's very minimal considering this has been my daily-driver for several months: