I haven't read the entire thread, but wanted to share my personal story.
For DS, every day I breastfed was too long for him, so for him, it would have been better for me not to breastfeed him at all. And i wont be putting my bellybub to the breast even a single time. So, there is no too young age for my children.
Now before I get judged, and frowned upon, let me tell you, I was given the all clear to breastfeed while taking lifesaving medication. ALL the studies said it was ok, ALL the health professionals said it was ok and encouraged it. Well it wasn't and it made my DS very very sick, and we still don't know if there have been any long term complications. After my sons reaction, the guidelines for the use of this medication in BFing have been changed. So, I really dont think we can say there is any 'too young' age. Every feeding relationship is unique and altered by any number of factors.