Posting a not-so-great experience, which hopefully might help a few other people to avoid. I have been waiting for funds to arrive from Australia, in order to apply for a non-O and after that, a retirement visa. The funds took longer than expected, and my "15 day" deadline for applying arrived.
My current visa is 60+30 days; I was told that i may be able to get an extra 7 day extension. So off I went to Immigration, and HOORAY!! - I got the extra 7 days. Plenty of time now for the money to arrive and apply for that non-O. Ah. No. I explained at Immigration that I just needed a few more days, and I would be applying for a non-O. What I was NOT aware nor informed of, was that after two visa extensions, you cannot apply for a change of visa. I found that out 10 mins too late.
Good luck to everyone else, hope this helps someone !