How quickly should oil pressure come up?

filter media breaks down when submerged in liquid like acidic suphurised old oil

in theory short of the glue going off due to humidity ( i presume you don't live in a rain forest) NOS should be fine.
it is unlikely that the anti drian back valve would degrade too much, thats the only rubbery bit in there, UV light and heat tends to play a part in rubber degredation. so if its sat on a shelf in its box in a store room or garage it will probably be ok

change a filter and oil on a barn find...that filter has probably broken down.




Dave