See, you totally don't have to be "Mini" for mini-sessions! I love photographing older kids and I often feel like these are the times parents look back on a feel like they missed the boat on photography. When we were little there were 'baby pictures' I think one random family photo where I remember looking at my mom and thinking she looked like a model or actress then.... nothing.
I don't know why it stops. It has always baffled me. I think the days of 'mom-daughter glamour shots' has to come back or something to save us from this halting of tween/teen/family photos that seems to come to a screeching halt sometime around 10-12 years of age. Okay, that maybe the glamor shots are over kill but I hope when my clients kids get to that age they still love seeing them on their wall because look at these two, they are gorgeous and who wouldn't want to always have their art? Thanks U family! You certainly have lovely kids!