These are Stage 0 + 1 car seats. They don't necessarily go to age 4, but up to a certain weight, when your LO reaches that weight limit will depend on how big they are. I have a friend who has one, though I think she didn't get it from birth, but at some point later. But her daughter is pretty big (in the 90th centile range) and is 2.5 now and just about to outgrow the weight range. I know that Maxi-Cosi does a few of these sort of combination car seats (that's what she has). The only things I would think of would be making sure it has the option for extended rear facing until the end of the weight range (whatever that might be). I would want to have the option to stay rear facing in any seat I bought. I would also think about how important it might be to you to have an infant seat you can take in and out of the car. The problem with these sorts of car seats is they are the kind you sort of leave in the car and can't really remove with the baby in them. That's fine for a toddler, but with a baby, I would want to have the option for a infant carrier type car seat that has the handle. They sleep a lot when they're little and you won't necessarily want to be picking them up out of the car seat and waking them up every time you need to go in and out of the car, especially in cold weather or rain or snow. Having the option to have something we could carry in and out of the house, put in a shopping trolley or attach to our pushchair with our daughter still sleeping in it made such a difference. You honestly cannot appreciate how amazing it is to do your food shopping with a peaceful sleeping baby instead of one that's been abruptly woken from a nap. So that would be my only caution and it's the reason we don't have one of these.