This has been a great year for games, and ideally, it should translate into a great year for game expansions, but not necessarily. I've probably treaded this water before (and I probably will come back here again), but I need game developers, or their accounting department to understand how i want to give them my money.
First, If you make something, and you make it well, I am likely to want to return for more. However there is a set amount of time between when you make it, and when I return for more, that allows me to feel like you have actually been making something, not that you just didn't give me everything.
There are alot of games that fall into this market, but most notably Battlefield:Bad Company 2, and most recently Fable III. The first promised map packs to the veterans (people who bought the game new), but only gave us maps we already had (physically!) on the disk, that were rehashes of maps already being used. Yes you read that right. We got to play maps for new scenarios that were just maps form other scenarios. At least Fable III was able to say, here's a zone to do a quest in a place you don't need to go. I know you don't need any DLC, but when you release something this quick right after the game came out, it was either unplanned or unfinished. I'm sure I'll be letting you know one day when I'm bored.
Second, Don't just throw anything at me and call it premium. I care about the games I play. I want to enjoy them, and I am very selective about which one's they are, and which one's they aren't. Here's a few samples of companies doing it right:
Rockstar with "The Lost and the Damned" and "The Ballad of Gay Tony". (I know those are from last year, deal with it.) Bioware with Mass Effect 2 and Dragon Age content. These guys added content that was worth the price (especially important) and added to the original packaging.
And Finally, consider when an upcoming game should be DLC versus a full package. The Force Unleashed II, this one's looking at you. You're way to short to be a full game, and honestly, I'd have traded the 3 DLC from the first game for your main game minus the trials. It's a better deal for my money.