Convertible seats stay in the car. I found the travel system to be worthless, we used the stroller maybe 3 times and as soon as she got to be 10-15 lbs it was horrible trying to carry her in the infant seat so we just ended up switching her to the convertible anyways. This time we bought the graco 4ever seat.
Convertible carseats do not come out of the car to click into the stroller. Only infant car seats do that. Convertible car seats have nothing to do with the stroller.
Travel system all the way!!!