I dont work for AKSA or NSWKBA, but my understanding is Yes, the insurance has a fixed 'anniversary date'. I assume this is because it is one policy, that can take on new members, rather than individual policies for each member who joins.
Better off being covered, regardless of the additional few $. All you need is for your kite to hit a car, or damage powerlines, signs, anything over the value of $60 to make it worth buying now, let alone hitting someone which could cost millions...
Just came back from overseas where I was a ski instructor, and we had to have $100mil coverage under the concept if you 'took out' some bigwig boss of a company, their family and company could sue you big time....
Email the www.nswkba.com.au team, and I'm sure they will have an official answer.
... DZ