The latest-generation DPFs tend to be a catalyst-coated matrix, these don't use a fuel additive to help the regeneration but instead rely on the catalyst coating in the DPF to lower the required reaction temperature.

When you're driving with engine fully warmed up (i.e. has been running for over 10-15 minutes) and with engine rpm above 2000 and usually above about 40mph, the exhaust gases will heat the DPF enough for regeneration to occur "passively". That is, the DPF is hot enough to start coking the soot to ash.

I've seen data logs from a Skoda Superb that shows under these conditions, the DPF will go from a 50% soot-loading to under 5% (i.e. a complete regeneration) within 6 to 7 minutes.

So if you're cruising at above 2000rpm on a motorway it will regenerate quite quickly. High loading and rpm will get the temperatures up quickly, but once the burn starts it will continue, you don't need to keep thrashing it.

You get 'active' regeneration when the soot loading in the DPF is high (over 50%) and the car isn't being driven in conditions that would allow a passive regeneration. Active regens use extra fuelling (so some unburnt fuel gets into the DPF and ignites). It is these active regen cycles that can get interrupted by switching-off the engine mid-regen, etc.

My own Mondeo 2.0 TDCi with DPF is used for mostly short trips (under 5 miles) with occasional longer blasts, and is fine. My tip is keep rpm above 2,000 on any open-road journey -- this is in the peak torque band so it's good for responsiveness and keeps the DPF clean.