The star awards issued through Airpoints are refundable less a small fee as long as cancelled prior to departure of the first sector. They can also be changed prior to departure, again for a small fee.

I think this is a great way to use airpoints, and long may it last at the current rates. As has been said there are some airlines with close to zero availability ever, but others have plenty of availability. It is up to the operating airline to decide how many seats to release to the rest of the star alliance and indeed whether to release any at all.