I think there's too much variation for there to be a "normal". The "normal" might be taking the chairs of the progressive line one per year (5-8 years depending on lodge and jurisdiction) but I get the impression that happens well under half the time.
When a Brother memorizes easily plus his lodge is having line problems it can be as short as 3 years.
My first time through the line was JS half year, SS, JD, SD, JW, SW, MW them relocate out of state about a year after leaving the east. Seven and a half years from raising, eight and half years from initiation.
My second time through the line was JD, JW, WM (you might think that's 3 years but the list does not end there), then WM again, TL, SD, SW for 7 years in chairs. I have no idea if that counts as once in the line, twice in the line or just a bizarre path of place holding assignments since I'd already been through the line before so I didn't need to do the entire sequence again. In the end I filled most of the chairs in that sequence.