How long in each car seat?

Hi Mommas! I’m wondering how long your babies stayed in their infant seats. My son was really tall and we transitioned him into the convertible seat at 6 months, but my daughter is much smaller (only 50% for height instead of 99% like my son) so I’m hoping she can stay in it longer. We have a Nuna Pipa if it makes a difference.

Also, my son is 4yo and still in his Nuna Rava. How long do kids usually stay in their convertible seats? I’m wondering if I’ll have to buy a second convertible car seat, or if my daughter will just be able to use my son’s when she’s ready. My daughter is 2 months old for reference. Thanks!