PI, do you realise that if you keep refinancing to IO, the term is effectively infinite? WHY do you prefer an IO with 100% offset? What happens if you want to buy a PPOR or buy another IP?
You're asking a lot of questions, getting lots of good answers, but I don't see the evidence that you understand what people have said. It's like people giving you good booze. If you don't know how to mix it properly, it's going to taste like turps.
30 year, IO is a contradiction in terms. An IO loan is eternal ie it NEVER gets paid off. For it to be a 30 year loan it must reset to P&I after some years and then go to a higher payment than would otherwise be the case.
Even my Macquarie LOC reset eventually to where I now pay down the principle.
Ok if your talking about an investment property there are several reasons why you would do this. The main benefit would be to pump all spare cash into your PPOR and pay it off sooner ( bad debt). Or you may want to pay the min amount, save into an offset for other investments. Having ready cash to go unconditional is a good tool for negotiating.
Unless you rent yourself and have investments this is most peoples end goal. There are many other tax related issues for investment finance, moving from one place to another and keeping the existing etc. You really need to see an accountant and then your broker. As while the broker cannot give tax advice they will understand what the accountant recommends.