Besides, if you read my post, I'm not that interested in mpg. I'm hoping, with doing short journeys, it may help to keep the DPF in good (better) condition than it might be.
As its quite low miles, I wouldn't be overly concerned, just read the handbook for what to do when the light comes on. If it was 80-100k miles, I'd probably be more concerned. It will need some regular longer runs, and ideally you want to let it regen long before the light comes on.
Also, service regular, and ensure you use the absolute correct oil for the engine, not just any old stuff, as the oil mixing with the unburnt particles is likely to cause a faster demise.
Just us a low saps oil, changed regular, if you have access to truck spec oils, they are low saps, as most HGV are euro5-6 now and use adblue and sccr,
Haven't a clue when mine regens, the V4 Volvo has a light on the dash which tells you its re-gening, but were doing lots of motorway miles, so not an issue.