only once they reach the weight limit on the seat, DD1 was 19-20 months before she hit the limit on her seat, we just had a mirror for her to look at and toys, after watching the links a couple of years ago that Melbel has put links to we wanted to keep them rear facing for as long as possible. I think their safety is paramount, rather than a change of view, if they are "bored" or what "other" people expect or think you should do. The video evidence really says a lot.

