When new mine did a regen once per tank, now it does it twice per tank, with no change in driving habits or loading. Soon it will spend as much time in regen as not. I can't get near a dealer because all their diesel techs are booked up weeks in advance. When I asked the service writer what were the reasons for the backlog, he replied "same as yours".
DPF/SCR technology summarized in three words: It doesn't work.