With our two biggest markets (Jevco and Royal & Sun Alliance), insurance experience/history doesn't really factor into the rate, unless there were prior motorcycle accidents and/or cancellations for non-pay. They rate more for the type of bike you ride and how long you've had your M-class licence. Also, as jeffjones pointed out, most of the premium is earned in the first few months - for example, Jevco retains 100% of the premium after the first 151 days - so essentially if you only have insurance for 5months, you still end up paying the full year rate, which makes sense as the premium is earned for the riding season. (for 30days of coverage they retain 15%, for 90 days 49% etc..)
If you plan to ride for at least 5 months in 2012, then it really makes no difference whether you get the policy in January or May. If the bike is valuable and you're concerned with fire&theft during storage, you may want to consider setting up a policy sooner rather than later, but if you're only planning to have liability on it anyways, it's entirely up to you when you wish to start.
