It also depends on your playstyle, how thoroughly you play the game :
only the main quest and a few side quests or searching every inch to make sure you find ALL that's in the game, secrets and maybe easter eggs too.

Plus:
the REPLAYability of the game is for me also important, but so far all Larian games I've played have a very good replayability. and are very addictive too grin

I'm 200% sure Original Sin will have a very good replay value !!
And the Editor in mind ... it's forever big fun ! claphands

On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin,
it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !