my car (Hyundai ix35) does a regen around every 100/150 miles, i keep the trip on instant mpg, when it regens mpg drops from 50 to around 28 mpg, it lasts for 10 miles
the one that trips a lot of people up, defantly with vag group and i think a few others is they need at least 1/4 tank of fuel in the tank to allow a regen to happen.
i think one of the magor problems is numptis buying hig output diesels and not driveing them hard enough or giveing them chance to warm up,
varible vane turbos need working and dpf's need getting hot to work and stay working. all the diesel cars i know that get driven hard have never had egr, vvt, or dpf problems