We have 4 carseats and one booster - 2 cars, 2 carseat aged kids. Should work, right?
It DOES work, except when DH puts the extra seat in his trunk "just in case" (just in case, what? In case you adopt a kid while driving to work?) and takes the booster out of my car to give to his parents, so I don't have to move it to their cars tomorrow.
In the grand scheme of things that I lift daily, a carseat is peanuts. Being stuck with 2 kids , 1 seat and a meeting that I must get to an hour away? Total pain in the arse!