[nabs]

If it was a mutual breakup due to an understanding on where you both stand in life at that point. And then you guys have had enough time to mature out of that stage of your lives and enjoy each others company, I don't see anything wrong with it.

This is maybe one of the only exceptions I would have to not dating an ex. Because really back then you just weren't ready for each other, and you both understood it, and now you just might be! As Berz said, there's no "loss of trust" issue, or any "craziness" issues, you continued to stay friends even after a few years of no contact. If the feeling is mutual then go for it.