much depends on the type of hub - i can easily produce 3 hubs in a coupla hours for recipes - especially if i already have the basics on file. I did this just a coupla weeks ago to answer a question about using oranges for non-dessert recipes. I just had to search my database of unpublished recipes.
I've got dozens of other proto-hubs waiting to be developed, so there are several topics I could write quickly
another type of hub would be travel hubs where i can break the trip into multiple segments. here i start with my journal / notes, then select images, create a map and can write several hubs fiarly quickly
i rarely start any hub totally from scratch