I don't know if this would be ok or even useful, but I wondered if it would be a good idea to list your breed and your experiences of length of pregnancy.
I see on here people with toy breeds for example saying they usually whelp early and wondered if a thread with a list would be interesting/of use to some people? I can't find my copy of book of the bitch but remember that gives birth weights, I don't remember if it gives typical length of pregnancy?

Pomeranian's normally day 59 but have had them day 63 and 64 with no problems, also had them a week early.

My Spanish Water Dogs can be anything from a week early to 4 days late with no problems.

Chihuahua Long Coats day 56 more often than not.

Is that the same for smooths?

I don't know!  :-)  (I don't like the temperament, so have never kept them!)

My mini longhaired dachsies have delivered 2 days early to 2 days late of first mating.

I can't find my copy of book of the bitch but remember that gives birth weights, I don't remember if it gives typical length of pregnancy?

It does for a selection of breeds.