I spent some time preparing this response and got interrupted by other things before I could finish it and post it. I realise the conversation has moved on in the meantime, but hopefully you might still find this of some value.
How do you recognise brumation? For many, the term ‘brumation’ conjures up images of a reptile being totally inactive for three or four months during winter, until the weather begins to warm up in spring. Yet this is not necessarily what happens. In nature, many reptile species come out and bask on sunny winter days. They may even drink. What they won’t do is eat. So to avoid confusion and yet answer your questions, let’s just talk about cooling, rather than brumating.
With the possible exception of the Diamond, cooling is NOT essential for Oz pythons. However, if you intend to breed them, then for most species cooling is recommended. The reason for this is that cooling can considerably increases the chances of breeding success. This is a generalisation and you will get exceptions to the rule. In Australia, cooling is most appropriate for the months May to July, although August is sometimes included. Partial cooling may be done in the months either side of this period, but there is no evidence to suggest this is any more effective. A lot of keepers who do not intend to breed will still cool their animals over winter. The reasons for this vary, such as: it provides a more natural yearly cycle; it allows the keeper a break from feeding and cleaning; it can save on heating and feeding costs; or any combination.
There are two main ways to go about cooling. The simplest approach is to reduce the running time of the ‘hot spot’ heater during the cooler months. The other main approach is to reduce the maximum temperatures reached during the cooling period. Clearly the second approach can only be implemented where one has variable control over the temperatures in the enclosure, such as via a thermostat.
The most difficult question to answer is how much cooling i.e. by how many hours should one turn off the “hot spot’ heater; by how many degrees should one reduce the maximum temperatures? If you asked 10 different people, you may get 10 different answers. This is where researching reliable sources comes into play. Make use of books and the net, but be selective. Restrict yourself to authors who have the runs on the board. Do not expect total agreement, as there is more than one way to skin a cat. However it will give you a ‘feel’ for an appropriate range within which to operate.