We too are permanent GNs, and our way of dealing with the "not on a holiday" and seeing an area for more than 6 weeks is to advertise your self as advertising.  We advertise on the Grey Nomads classifieds (for free) and are rarely short of a house sit.  We are currently house sitting at Hatton Vale for 6 weeks, have another at Goomeri in February for 7 weeks, followed by another near Inverell for about the same time.  Currently trying to fill in the gap over Christmas/new year. 

Some sits have been for as little as two or three weeks, but, hey, better than caravan parks.  Helps if a) your caravan is self contained and b) you are happy to sit a house with pets.  Apply for a police check (for both of you) and in the first instance, get some character references.  As you start getting sits, collect references from the home owners.  Check out some of the advertisements here....

http://thegreynomads.com.au/classifieds/housesitters-available/

Start with basic (easy) house sits.  Farm sits are good fun, but a little more complicated until / unless you get/have experience. Good luck with whatever you decide. Believe me, we just don't have enough weeks in the year, we have flicked off two sits to another couple, and another has tried to send some our way.