the Australian team has been ageing for a while but its no big deal and in my view is part of the reason Australian cricket has gotten so strong. Time after time players have shown you can play the game at your peak right into your mid 30's.
There is no doubt that the first generation of professional cricketers pushed the ages up as they held on for longer in an attempt to capatalise on their success - i dare say guys like Mark Taylor, Matt Hayden, Mark Waugh, Ian Healy, Steve Waugh, Shane Warne, Glenn McGrath would've left the game earlier. Whilst even the support players got older - Darren Lehmann, Michael Kasprowicz, Brad Hodge, Martin Love, Andrew Bichel etc,.
But i think its been good for Australian cricket. Gives player more a chance to develop their game before being thrust into test cricket.
the kind of timeline players follow now is:
18-22: first class development
23-26: establish themselves as permenant first class fixture
27-28: hit the top echelons of australian first class cricket
29+: just keep going and wait for a chance to play international cricket
there are obviousbly a number of players who have jumped the queues but there's not many - Clarke, Watson, Johnson and Tait the most obvious examples... but of those 4 only Clarke has established himself in the test team. the other 3 have just had a taste and nothing more.
and it's good for the selectors cause it gives them a good time frame to see a player develop and make sure they are picking the right player rather than just taking a gamble on some flashy youngster with 10 good games to his name.
Compare it to the timeline of some other countries, particularly the asian countries where they tend to be very youth orientated:
16-18: get into the first class scene
19-22 yo's: have a good season in FC cricket and suddenly your nearly, or you are, playing test cricket.
and if you haven't established yourself by the age of 25, then you are discared and almost certainly not going to be given a second chance.
the amount of young talent across the world exposed to test cricket at an early age and then just broken because they weren't ready is ludicrous and IMO is one of the biggest reasons Pakistan and India (two cricket mad nations which should be at the top) have not given a more serious challenge to Australia in recent times.