For stir-fry I usually use peanut oil (for other things like meats canola).
As for whether to start over, I suppose it is about the quality of the current seasoning. If the thickness of the chipped off areas is substantial, that would indicate way too much oil was used for that seasoning, and I would scrub it off and start over.
When seasoning, the coating of oil used should really be super thin. Like I mentioned above, I use a cotton tee shirt to literally buff off all the oil before popping them in the oven. It should be hard to see or feel. I keep the same tee shirt in a metal bin in front of a sink drawer.
Too thick a coating of oil can chip (and even become rancid) as it prevents proper polymerization of the oil to the surface of the pan.
Like lacquer on a cabinet or automobile, many thin coats is way better than a thick one.
