I wouldn't say anyone's bagging Canterbury either and that most likely all of us here are happy to see her doing great work and into the future.
It's more, speculating on a potential Endeavour replacement and whether there are merits in operating a type of vessel that could also fulfil the eventual Canterbury replacement. A key factor may be operating costs and savings eg reduced training and logisitics as stated by Lucas (assuming that can be achieved in comparison with two seperate types of vessel, although that additional flexibility factor of a common type would need to be quantified too). Bear in mind VfM exercises will no doubt be a permanent, regular fixture, accompanying these proposed 5 yearly Defence Reviews (2015, 2020 etc).
Eg if Canterbury entered service in 2009 (initially to be 2007) and is meant to have a 30 year life(?), then in simple terms the mid-life point may be 15 years on from 2009 i.e. 2024.
As the DWP is planning out until 2035, it could very well be that 2024 date (or thereabouts - even if it were 2029 or 20 years of life) is being factored in by the planners as being a point to weigh up whether to undertake a MLU or early replacement.
If by chance this happens to be so, and if it happens that Defence planners wish to weigh up whether an Endeavour replacement design could be something like the type of vessel Mr C has been suggesting (mini-MESHD or even a JSS etc), then there's no harm is us here undertaking this type of discussion, which isn't bagging Canterbury, the Navy, Defence or the personnel who make Canterbury sail.
On the page before I've found some answers as to how much Canterbury can carry the typical "2011 NZArmy" and looked at the breakdown of the Op Hamel embarkment (it was at 105% capacity). It will be interesting to see whether these are typical numbers for typical CATG - Cav and CATG - Light Infantry embarkments.
Incidentally at 105% capacity it means possibly no (or not many) Huey helos could be carried in this instance (or if they were to be carried next time, then less additional Army vehicles can be carried etc) and would there have been room for a Seasprite, integral to Canterbury's ship-operations (i.e. as opposed to simply transporting Huey's/NH90's to accompany the Army, which don't always need to be carried and their place taken by vehicles depending on the make-up of the deployment)?
That may or may not (as in Army will no doubt have other configurations depending on the type of deployment) have some bearing on additional vehicle lane lengths for the proposed Endeavour replacement, assuming it may be a JSS of sorts, to back up Canterbury.
And also, seeing that it appears the Govt sees value in ensuring reliable sealift can always be available (I believe this has been suggested by the defmin or govt recently?), if so and they fund a Endeavour replacement, would it also need be capable of carrying the above typical compliment (as was Ex-Hamel's embarkment) if Canterbury was not available (eg in dry dock or on deployment elsewhere etc)?
Alternatively would the Army need to deploy a battalion or at least the vehicles (not necessarily the personnel), as inferred in the original sealift reviews of around 2000? If so, would a larger, JSS / mini-MESHD Endeavour replacement be worth investigating? Incidentally I don't believe the Endeavour replacement is meant to necessarily carry the troops (or am I wrong) just vehicles (and maybe a few helos), using port facilities (i.e. no Landing Craft). Obviously some big cranes would be handy, as there should also be space for containers, and should speed up off-loading (and then getting the ship the hell outta there again)!
One headache may be though, these JSS / mini-MESHD types appear to be in their infancy in terms of concept design (something that Swerve mentioned a year or so to be aware of), so timing may become an issue for defence planners.