A.
My two children have the Britax Marathon seats that get taken in and out of my car, our nanny's car and my husband's car throughout each week. It's just something we all have to do since we want one of the safest carseats, but don't want to buy extras. We are lucky that we have the LATCH system in all vehicles, but if we didn't we would properly train/learn how to install the seats using seatbelts in each car. There are many local places that will do this.