Webf,
Imagine going to your grannies house, getting her 1970s TV and putting it on the roof. Then subject it to very hot and cold temperatures and throwing in some salt water for added measure. 909s are heat sensitive and are maintenance intensive in hot climates. When you only have two, the loss of one is a huge loss in capability in what is an already compromised design.
With the exception of CVF, Adm West's comments make depressing reading. I'm pleased that the MoD has settled on a 36 cab/85 sorties per day capability for CVF.