Hmmmmm, good question. If only I took notes and recorded the dates. Well, I'll do my best at estimating times.
I think it has more to do with the quality of the stock more than anything. Good stock is fat, healthy, well-watered, and not woody. The best PC stock is about the top foot to foot and a half of a column. Below that, it gets pretty woody.
It also seems to depend on whether it's rooted stock or not. Un-rooted stock seems to focus on root formation before scion growth. Can they decide like that? Either way, once they start forming roots, the scions start growing. Rooted stock will show scion growth much faster, perhaps a week or so.
I've left un-rooted grafts in a cool, dark box for about 2 months before without any trouble. Once I popped them into some soil and put them under lights, they started rooting and a couple weeks later the scions started growing.
Pup scions seem to be the fastest. They show signs of growth consistently within a week to 2 weeks.
Tip scions usually start showing signs of growth in 2 weeks to a month.
Center cuts have taken anywhere from 3 weeks to 2 months. I'm guessing because they have a lot more "work" to do.
I've only grafted three crests and I don't remember how long that took. Probably close to a normal tip.
Happy Grafting,
Hcc