I'm not sure yet about sleeves either. I do have a couple questions though.
1. Are the "Standard Card Game Sleeves" (the Gray pack) from FFG the right kind to buy? It looks like you get 50 sleeves for $2.99. That seems reasonable.
2. Sort of a separate question: How does everyone store their cards? At some point, they can't all fit in the box, right? Do you get Card Boxes to store them? Or use zip-lock baggies? Just curious.
3. Is it more difficult to store the cards if they're sleeved? Is it also more difficult to shuffle them? Do they go flying and slipping around?
1. Yes, I got the FFG grey pack. They are the "right size" but they don't fit very tight. Still, you get used to it pretty quick.
2. The Core and Shadows of Mirkwood should all fit in the core set box if you invert the cardboard insert to create two columns. That's how I currently store my cards. I don't have anything beyond those yet, but I imagine you can fit a fair few cards into the Khazad-dum box as well. If it comes down to it, you may need to alter the insert in your core set box to allow three rows of cards.
3. I don't find slipping to be a big problem with my sleeved cards, but one thing you have to consider is that you need to shuffle at an angle at the bottom corner. If you shuffle top-edge-to-bottom-edge you will get card trying to fit into other cards' sleeves. Still, I was finding that I didn't get a very good shuffle with the card sleeves. A lot of cards stuck together. Recently I've started just laying the two halve of the deck side-by-side and merging them sideways, starting at the lower corner. This seems to get a pretty good mesh and doesn't require bending the cards. I miss traditional shuffling, but I can just get a deck of cards out for that.