Air source heat pump flow rate too high?

[RichardMark]

I have a Samsung Gen6 8KW air source heat pump. It works very well, but I noticed that my flow rate is between 28 and 31 l/m and I wonder if this is too high? The circulating pump is a Grundfos UPS2 (8m head I think) on setting 3 which I understand is suitable for larger heat pumps than mine. Is this flow rate likely to reduce the life of the ASHP? And is this efficient - would a slower rate actually be more efficient than this?
Thanks.