Traveling

Hey all so my mom lives in Maine and I'm in New Jersey. I'm planning to go up and stay with her for a few months (21 weeks now). We drive instead of fly so it's about a 8-10hr trip depending on traffic and all. I know I have to make frequent stops to move and walk around to stretch and get the blood flowing, my question is at what point in my pregnancy won't I be able to take those long drives?? I know for flying it's in the last 2 months so I'm assuming here's a limit for driving long distances as well.