Yes, 2 to 6 weeks is what i am seeing with sites that i am working on. A lot depends on how old are the sites holding top positions in this niche.It took exactly 4 weeks until the 3rd PBN link kicked in. It is a strong one and I paid some good money for it. I thought "man, what a waste" in the past 4 weeks. But yesterday it kicked in. The site jumped from #27 to #11 for an 15k keyword. The subpage was only 2 months old. I guess there must be an google filter for new posts too. Probably thats also a reason why it took that long. Back in the days, a new post was able to rank within days. Now they even put new posts in the sandbox for 1-2 months. At least in my experience.
What I wonder is, how much link juice do I miss when I use the PBN as a blog that does not show full posts? So no direct backlink from the home page. I have a feeling that it is a big footprint to show full posts and that they will start banning PBN with full posts soon.