Sounds kind of like the ol\' New Game+ they used to have. I must say though, I get tired of companies throwing in 20 hours of misc time filling quests to make their games \'longer\'. There\'s nothing wrong with a 10-15 hour game, that\'s a good 2 weeks for a normal busy gamer, and if they have re-play-through options, well....
I find with a lot of games that they \'make\' longer, I end up getting 3/4ths of the way through and then give up cause I\'m getting bored with the same ol\' same ol.