On a completely different note, I am hoping for the HMAS Success (18,000t) replacement the RAN looks at something like the Cantabria class (19,600t) or Berlin class (20,240t) rather than modifying a commerical design, which was done with HMAS Sirius.
from white paper
To be fair Sirius (25,016t) replaced Westralia (40,870t) which was built as a Stat 32 class tanker and modified for underway replenishment in 1979 for the British Royal Fleet Auxiliary.
http://en.wikipedia.org/wiki/HMAS_Sirius_(O_266)
Sirius is expected to remain in service for around 15 years, so is due for replacement around 2023.
It is interesting that Success will have been in service for well over 30 years, (quite likely around 36years) but the Sirius (which is a new ship) has an expected service life of half of that. Sirius may have been half the price and faster to get in service, but if there needs to be two of Sirius style vessels procured for the same service life as a ship which was specially constructed for the role, is there any significant savings?
If the Success replacement program commences around 2016, it is likely the vessel would be in service somewhere around 2020, which is around the time the Sirius replacement would need to start. Perhaps Success and Sirius could be replaced with a single design with construction of the 2nd getting under way after the first is completed.
It is worth noting that Success is an Auxiliary Oiler Replenishment (AOR) vessel whereas Sirius is purely an Auxiliary Oiler (AO) vessel.