I've owned an AU2 ex taxi, bought it in February, 2005. (It was only on the road as a cab from late 2001 - early 2004). It was so current in the taxi world that I actually managed to pick up passengers, without trying ;)
In Melbourne it is 6 years and 6 months. Disabled cabs get longer, could be 10 years from memory in Victoria. I recently saw an EF Disabled cab, but it could have been an EL with an EF front (making it at least a 97 or 98 model).
Had no issues with my ex cab. You can buy BA taxis now for $4000 if you look around.
It went from this:
To this (image courtesy of a fellow forum member - credit to him):
