I also think of "long" hair as being waist-length or longer, although I really like mid-thigh or so...

Not sure how to answer "how long is long enough?", but I can definitely answer "how long is too long?": Each person can only grow hair to a certain max length. Too long is when someone grows their hair to (or near) that limit, so towards the ends the hair gets really thin and wispy and straggly looking. In that case cutting shorter would make the overall look much better. You don't seem to have that problem - your hair looks thick down the entire length even when *really* long (you are definitely blessed with good genes in that regard!). So I say go with whatever length feels right to you, you will always be a "long hair babe" in my book!