How quickly should oil pressure come up?

Wow, I've really sent you all down the rabbit hole. One of the things I love about this site. Thanks again for all the responses as I never had any idea the composition of motor oil was this complex. I'm assuming that seeing different pressure results across brands at the same oil weight is not out of the question depending on the additive package used in each? I'm really starting to wonder about YY1's comment about the possibility of the oil breaking down even though there's only 1200 miles on it.