When to move up to the next raid

I like this post over at Tank Like a Girl that raises the question of just when your guild should make the big step to move on up the raiding ranks. Just last night, my very casual guild headed into Ulduar for the first time, and even though we'd never been in there before (we've been doing Naxx, OS, and EoE with some regularity, though when I say we're casual, I mean we're really casual), I think we did it at exactly the right time. We made it up to Kologarn -- enough to know that we didn't go in too early (and come out empty-handed, unable to down any bosses) or too late (and breeze through the place).

Now obviously, every guild is in a different place raiding-wise (and most guilds are way ahead of ours, I know), and TLaG is dealing with a different dilemma: whether to take down Yogg-Saron before moving on to ToC or not. And in her case, she's got the added "gotta catch 'em all" thinking. But it's a tough thing as a raid leader -- you don't want to move on past content you know you can do eventually, and progression always beckons. In the end, you've got to figure out what's best for the guild. And of course, the content's not going anywhere -- if you can't drop a certain boss this week, there's always the next raid reset.