I love RPGs and this is definitely one of the best I've ever played. A true successor to Baldur's Gate and as immersive as Final Fantasy 7 was in its day.
You can replay it endless times given the ability to play the different origins and the different character types. I had over a hundred hours on the main game including the DLC you play as part of it.
Then you've all the stand alone DLC. It's truly epic and for nothing at the current price.
The decisions you make affect how the story develops - it's just brilliant.
When you buy it, you'll be able to access most of the DLC in game once you reach a certain point. Leliana's song can be played before or after the main game (after is best in my opinion) and The Darkspawnn Chronicles should be played after you've beaten the game. The others are best played in the following order: Awakenings, Golems... and finally Witch Hunt. You can import your character into these 3 or start afresh.
If you get to bed by 2 you'll be doing well :-)