If you have to tell them that you are 'leaving' an altitude when you are on RADAR why would you not tell them that you are 'maintaining' an altitude as ATC seem incapable of monitoring it themselves. Whilst we are on the subject why does Oz ATC use 'to' in altitude clearances e.g. Descend to 2500 feet. The rest of the world has stopped this practice and just says 'descend 2500 feet' to avoid any confusion
