I made a trip to campus once every 3-4 weeks. I think I made 6 trips to campus the first semester. Classes went from like 9-2 if I'm remembering right. I'm going back in January to finish the last semester because I got a M-F job who said they would work with me so I could go then I could never get the time off. Now I have a new job where I have the time to go :)
You may want to stay on for 90 days just in case, but I would tell your DON that you still plan on leaving. I recently had to do the same thing because my former employer really needs the help but I don't plan on staying on prn but a few months.