Do it. But be careful, it might ruin Hawaii for you forever.
I love Hawaii. Totally love it. But if I ever lived there it would be part time. You will get Island Fever (instead of cabin fever) unless you really enjoy the quiet life. Some people do. So it's just something to keep in mind. 3-4 years sounds perfect. I like Hawaii in spurts. Because I love my city life too much.
I would be afraid of getting island fever, but it definitely wouldn't be due to missing the city. I grew up in a town of less than 15,000 and had been to a large city just a handful of times before I went to college. I live 30 minutes west of Denver in a small town and aside from work, I rarely get near it.
What might get to me is the inability to take road trips and the like. You can get from one end of Kauai to the other in about an hour, even with the slow speed limits. After a few years, I think I'd be ready to come back to the mainland.
We'll see if any offers get extended. If not, then no worries anyway.