Hi. I have posted this in chat but it was suggested I post here.. Ds 3.5 is currently in a maxi cosi stage 1 car seat. Last week i had a high backed booster seat in the car because i was lookng after my neice. Ds was very interested in it and asked if he could sit in it because his car seat is too small. He has never mentioned this before so think it is just an excuse to go in the 'big boy seat' Ds is just 100cm tall and weighs 38lbs (just under the 18kg max weight for his current car seat) so i guess it is time for the next stage car seat. I just feel so much safer with him strapped in with the harness rather than just the adult belt. Next question, the high backed booster i have in the car is dds old hbb, it is about 8 yrs old so i am guessing it needs to be replaced rather than ds being able to use it? (It is only used very occasionally for my neice 7yrs on the way home from school which is about a mile on quiet roads but would obviously be used much more for ds on busy roads and the motorway). Dp thinks it will be fine but i am sure i have heard about car seats having a shelf life but not sure if this is just the earlier ones? It is a graco sport (i think) Final question (i promise) ds has always had an isofix car seat, i have been looking at the maxi cosi rodifix hbb with isofix which looks good but the rodi air protect seemed to get a better which rating, do i need an isofix hbb or is the other one just as safe? I suffer from anxiety at the best of times but need to feel safe with ds in the car.