Thanks soulighter and stevejnr for your posts.
I've retained QF silver for the next year (my renewal date is the end of May) and already have a number of flights ticketed for QF so should make gold next year.
My credit card in Singapore earns me Krisflyer miles but flying on SQ metal out of Singapore for some reason is usually double than any other airlines so think I will stick with Air NZ Airpoints.