So my oldest is in a booster, she's 7, 54lbs and 50IN tall. She is in the evenflo big kid booster (but I tried her in the turbobooster, and had the same problem). She still has some height in the booster, BUT if it goes any higher in my van, it will be touching the ceiling. Is that safe? or at that point would you put her in a NBB? I'm guessing it will be a year at least before I move her up again, she just moved up yesterday. (unless she has some random growth spurt). I don't know, WWYD? I have a harmony literider that she uses for the once a month (if even that) trips in my husbands car, and would be willing to eventually use that when she outgrows the big kid booster.