...from infant car seat to convertible car seat?  I know that most convertibles can actually be used from the newborn stage, but it's easier to have the infant car seat b/c you can carry LO in it.  I also know that infant seats have weight and height limits.  At this point, I'm not sure if DD will reach the weight or the height limit first on her infant seat.
                
                             
        
Re: When do you plan to transition...
I am hoping J will be sitting by then! He may hit weight first (22lbs... he was over 16 a week ago) I have already realized he is too big to be carted around in the bucket, and only do so if he is sleeping... otherwise I try to wear him.
I bought our convertible on sale... so although we should get a second for our other vehicle we won't be in a mad rush when it is time to switch. I would say after he is sitting, but probably by 8 months?