I would start to pump and freeze about 2 months ahead. Friend pumped in the middle of the night for 2 weeks for a weekend trip, and then she pumped and saved on the trip. I would not skip pumping. It will seriously impact your ability to nurse him when you return. If weaning is not an option, then you need to ensure arrangements to pump so you can return to nursing when you come back.
All babies are different, but my DD took 12ish ounces after 6 mo. old for a 10 hour day (travel time and work day). I would pump your regular schedule and then add at least 2 more to imitate his feeding schedule.
Also, if you go, find out your rights re: traveling with milk without the baby on an airplane. Some TSA do not know that it is currently allowed. Have a plan B, like mailing it home UPS if necessary.