I’m not sure what the cost is in Australia, however in the USA the cost is nil – there is no requirement to renew an instrument rating. It is ever lasting as long as you keep up the recency requirements – which are less costly than Australia.
Isn’t it interesting that the USA, with its terrible weather, does not need the enormous impost on the industry of instrument rating renewals?
Ok, I'll go against the flow. I don't like doing renewels as much as anyone else, but I always learn something and I have absolutely no doubt that I'm a much sharper pilot for having to do one every year along with a prof check every six months.
The interesting thing about us having a lack of terrible weather, particularly in the north over the dry season is that we all get woefully uncurrent because we don't see a fricken cloud for six months. So I think your logic is backwards. The worse the weather you see, the more likely you'll be current and not need a renewel.