On my FEC-100 I scoop out the burnpot with a tablespoon before startup every cook, and scoop up what is laying on the floor of the cooker as well, or if soiled with grease I change the foil I keep on the floor. This is because it is all easily accessible, and there is generally some ash left in the burn pot after the remaining pellets burn down.
When I had my Traeger, maybe once a month I would take it apart and clean it, and that's mainly because it was a pain removing the grates, drip pan, and heat diffuser to get to the pot. Honestly it didn't seem to cook much different after cleaning the pot, so I had no real encouragement to do it more often. Add to this, I updated to a later Traeger controller with a shutdown cycle, so after doing this the pot was always nearly empty when I checked, so I stopped worrying about it.
When I had my LG, the grates were easier to remove because they were split into 3 of them. The drip pan could be lifted with one hand, while the pot was inspected. I say inspected, because the pot never had any leftover ash in it due to the shutdown cycle.
Now with my PG500, when the fan kicks on, there is a small burst of ash out of the firepot, from the last cook, which settles outside on the removable ash tray. Note the PG500 is like my FEC-100 in that neither have specific shutdown cycles to burn the leftover pellets and blow out the ash. I empty the ash tray every few cooks when needed. The fire pot is pretty easily accessible, so if I wasn't cooking on it several times a week, I might be more inclined to lift the grate and the deflector (both very easy to do), and scoop out the pot just so moisture in the ash doesn't make it crust over such that it would not blow out on the next usage.