R.Y.
My son is younger, 4.5, but we got the Nautilus over a year ago (almost 2 years I think) and he still likes it and fits fine. He was 40 lbs when we got it and is now over 50 lbs and at least 2 inches taller. Also he now can buckle and unbuckle himself most of the time. We really like this seat (we have 2, one in each car). My little one likes it too (20 months and just over the lower weight limit). She only rode in it once in a minor crisis. It works out for us since if my older one outgrows it my younger one can use it.