The Socceroos' last fixture saw them hoist aloft the Asian Cup trophy after a 2-1 extra-time win over South Korea in January.
But ahead of this week's meeting with the world champions in Kaisersalutern, Postecoglou insisted Australia are targeting further improvement.
"In isolation our achievement is great but if you don't build on it, you miss an opportunity," he said.
"We've had great moments in our football history before and we've capitalised on some of them and some we haven't, so it's up to now the responsibility of the national team but also everyone involved in the game to continually strive to better and hopefully improve the status of the game in the country.
"We are extremely pleased with how the Asian Cup went and extremely pleased to have won the competition on home soil.
"I thought our performances were very consistent throughout it. You move on pretty quickly in football.
"All the boys have been back at their clubs and getting stuck into their club football.
"We know there is World Cup qualification on the horizon and it's a great fixture for us to really measure ourselves and another great test for a lot of the players in this group.
"You feel good about what has happened but for the most part we have moved on from it."
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