I clean my uds out after maybe 10 or 12 cooks, just cooked a pork butt yesterday and its getting close to needing dumped. I have never had a fire, and I have loaded it with charcoal and wood way more then needed, never have bothered, to count anything, then used what was left for the next cook. So I don't think you can load to much if you are maintaining good vent control, and not letting the fire get to big before hand, its much harder to control if you do. As already mentioned get in and out of the uds fast or the fire can flare up and maybe catch grease on fire, I have never had it happen, in fact I sometimes leave it off longer than normal just to get the fire up a bit. I don't use water pan or diffuser, just the basket of fuel, and I cook around 250/300. I know nothing about the mini.
Let us have a drink and by God lets us not think about the things we ain't never going to know about.