It depends on the thread's actual discussion topic.
Stupid stuff for people with shallow senses of humor (though those can actually be funny at times), picture threads, and drama usually has an exponential page growth.
Slices of someone's life generally don't have that page growth.
Philosophy is a bit of a weird one, half of the threads grow fast and the other half don't.
>ACTA is a widely discussed thing on the internet
>thread scraped together 4 pages over 2-3 days
>totally
You see, people in the U.S. are a lot crankier, so SOPA is discussed more in these forums. I don't think the majority of users are in the U.S., but a lot of them are.