I dont know Dave
All i can offer is provided the coolant is kept above 78 the DPF will continue to function.
I also replaced my stats and now achieve 91c every journey. It warms within 10mins to regen temps (low 80s) and it will take a further 5 mins to reach 91c.
If the car is taking longer to warm up but is still achieving > 78c you still may have DPF issues if you don't drive it for long enough.
I know you are probably aware of this
The only other thing i heard was BMW didnt put a temp gauge on the 335D because it can vary so much. It can range from 78c to 90c when doing a regen so such a fluctuation is either going to alarm customers and create unnecessary panic or BMW would build in a buffer which is just pointless.