i found this timeline. i think its very acurate according to the few stories ive heard.
http://www.iskcondesiretree.net/profiles/blogs/shri-krishna-life-timeline-on
all the tales related with gopis were perfomed in the stage 7-10 yo!, then he killed kamsa and moved to matura, or something. he finished his stage as a cowherd and begins to be a royal. i found this painting, done by western artist, i thing is much more accurate than indians. indians paintings were done around 400-500 years ago, when the school that supported krishna began more popular in india. these tales were supposed to take place around 5000 years ago
http://www.iskconhk.org/upimg/allimg/class01/1_060614030506.jpg
if you ask me if youth marriages are still practiced in india, ive got not idea, buy maybe in rural zones. when english came to india they westernize everything. one thing that horrorized english was the practice of burning widows alive along their housbands, practice that was completely prohibited.
youth marriages maybe controled too. great beliefs, interesting beliefs complex. original.