Can I please ask - how do you know that the DPF is doing a regen?
I can recall two occasions when I've pulled up on the drive after a 40 mile commute home from work (99% at 70+) and the fans take a good 5-10 minutes to shut down. Is this a regen taking place or just the cooling system being keen?
that sounds like a regen, but maybe the times you noticed it the car hadn't got warm enough soon enough, or I would have thought that it would have done it and stopped while you were still driving...