Members posting too much

[dturnbull]

I'm working on a new forum and it's going quite good, but there's a couple of members who are really "enthusiastic" posters. They're perfectly friendly and aren't exactly breaking the rules in anyway, but a majority of the threads end up being dominated by replies between both of them; it can sort of suck the community-feel out of the community.

How would you handle this? I've messaged them both individually about the problem, and they were fine with my critique, but there's still instances where a thread can turn more into an IM conversation rather than a public conversation.

I don't want to alienate them, because they are otherwise great members (they individually welcome new members etc), but they're just a little over-enthusiastic.