Well each time there's been a DLC added, there were new things added that made me want to start a new character and play through. That happened with Dead Money, then again with Honest Hearts. I was about to do that yet again right after I finished Old World Blues, but with Lonesome Road supposedly being close I kept that maxed character and used it to play through Lonesome Road to get the feel for it and to see all the new perks n stuff. So now I finished that I am going to start a new character and play through the whole game and all DLC. I know one thing, my character is going to be all 100's long before level 50 what with all the skill books each DLC adds. :)