Today we had Ari's new carseat installed by a professional.
Here is what I learned today:
Most cars' latch systems support a child up to 48 pounds. Once your child reaches 48 pounds, reinstall the carseat using a seatbelt. Or use the seatbelt the first time around if that is your preference.
We opted to use the latch system for as long as we can because people accidentally undo the seatbelt. It happened so many times with our infant seat! Reinstalling a carseat using the seatbelt is so much more time-consuming than using the latches!