True, it's younger and thus hasn't gotten as far out yet, but a *little* bit of advertising, like sigs on other boards you post on regularly, affiliate with bigger Simpsons sites (I'll add you to my links page in the next update)

I can see where you're coming from, that sometimes smaller is better of course. It's really all down to the target audience, in this case it's a collection of Lisa-nuts, I myself happen to be one, hence why I joined, The NHC is more for the general Simpsons fan, and my place is for just anybody with an opinion or a picture to share. 

This is a nice little community, I'll say that, but could always do with a little more coming in.

5000 is indeed a nice milestone, it just took a little longer than some would've seen really. There are those that wont join a forum (even if they find it interesting) if it doesn't look very active. (Not that I'm saying that LTS isnt of course )

This is just some advice, so feel free to ignore my last few posts, I'm just speaking as someone "In the business" so to speak.

ALM
I was far from idea of comparing LTS with other forums. Most of the forums I've seen (not necessary Simpsonic) are too crowdy, overwhelmed with kids and meaningless threads, so I ignore them. Of course they all have the right to live, Internet is for everyone, but I personally don't want LTS to become something like that. Read my first post - I'm glad not just because LTS has hit that milestone, but also because I see that most of the posts here (or, at least, very significant part of them) are good posts, are something interesting to read. That's not possible on big forums, from the certain point you have to choose between quality and quantity. And like others already said, LTS is a thematic forum, not a forum "about everything", and its subject is very special. I don't know how to make it 10 times more active than now without converting it into yet another offtopic forum.

Some advertisement could be a way, I agree with you here, but it should be done carefully. Public advertisement is an irreversible step, before taking it you should be sure it won't make more harm than good to the community.

ALM
Of course it's very personal. To me, a good post is the post that you like to read and re-read afterwards. It's hard to make a good post with short one-liner, and it's hard to claim a topic interesting if it consists of posts like that. Again, that's how I see things, someone else's vision can be different, and everyone's free to choose a forum he likes more. What I'm pointing at, is that there is a lot of "fast forums" already. They are huge, they are crowdy, they are mostly offtopic. I see no sense in making yet another one. I want to see something unique, something special, something that haven't been done before. And if we'll have to pay with lower activity for that - well, okay.

Nah!   The descriptions on the index page of the forum clearly state that they're not exclusively for Lisa stuff.   The one for the Lisa's Family board even says "Don't be afraid to create offtopic threads".   Anyone who dismisses the forum because they can't even be bothered to read few short descriptions isn't going to have enough sense to contribute anything worthwhile anyway.   
I think the board names are rather sweet! 
Quality beats quantity every time.

Yay

Yeah, unless you're one of those big boards that is actually on big boards (500,000 posts or more) then its likely there (10 times over )

In this case, I have to agree, that they could be just Yahoo bots which is the most common culprit. (If you install the "Googlebot and Spiders" mod you'll see what I mean.