I believe that even top posters won't be able to make 10 constructive posts in an hour because we as humans need to have some rest after making some posts.
I guess it would depend on the strict definition of "constructive". If that doesn't necessarily include post length, 10 posts in an hour is not only possible but I think I've done it before and probably others have as well. Sometimes there are discussions where there's actually back-and-forth conversations between members (which unfortunately isn't the case most of the time), and if that back-and-forth is fast enough, it'd be easy to make 10 or more in an hour.
I don't think rest has anything to do with posting. It's more a matter of finding threads that catch your interest and in which you can write something halfway decent instead of just writing a very generic, vague, and poorly-constructed series of words--and that's generally what burst posters do. I've seen them in action plenty of times, and I can say with certainty that there's only one exception that I've ever seen to that rule but I'll be damned if I can remember that member's name. He got called out for it, but the stuff he was writing was by no means crappy.
This the most important part of writing a good reply post to a thread. Find something you understand and can relate to. I am in posting and reading mode at the moment. I read 1 or 2 pages of a section. I look at 1 or 2 pages of my last posts. I look at the last 20 posts I merited and I look at the last 20 posts I got.
I read 3 pages of
meta
I read bitcoin discussion
I read economics
I read mining
And this can all take 2 hours time I may only find 2 threads to reply to. Or six or 7.
This is a routine I do 2 times every day so say 4 hours a day on the forum is very typical time frame for me.
But mining and gear sales is my business. They got slow and I opened a signature I do not do that very often.
In order to do a good job I spend more time looking for good threads .