Hi Mik68
My OH and I currently own a fifth wheel and TV in the USA (in storage in Phoenix). We have done two 12 month trips and plan on returning for another one.
We also planned on bringing a TT back to Australia and were quoted $25000 (3 years ago) for the conversion so we canned the idea. I would be really interested in who in going to do your conversion.
Also there can be some problems with entry visas so just be aware that staying for longer than 6 months may be difficult unless you plan on leaving and travelling into Canada or Mexico for more than 30 days.
We have licensed and insured our vehicles in Texas and use Escapees as an address and mail forwarding service. Without a residential address you are unable to license and insure vehicles.
Also, if you own the vehicles for less than 12 months you may also have to pay GST into Australia - might be worth checking on that if you haven't already done so.
Feel free to PM me if you have any questions.
Oh and by the way - we are in Perth too.
Cheers