went through the same thing with two daughters going to school but not the distance you mentioned.. one was 300 miles the other was 30.. LOL.. A car you have been wrenching on for years you know inside and out for the most part.. you have done a lot of preventive maintenance for sure.. If you think the CV joints need replacing I would get a good set off rock auto and change them out or take them off and rebuild or have rebuilt. not sure if that is a thing nowadays.. main thing is she gets oil changed when needed if find.. and is checking it as well.. Every time I would speak with the one 300 miles away I would ask, have you check the oil level recently?? they had a hat made and sent to me for birthday some years ago.. LOL.. good luck..