"Is it sensible to have a 'strategic defense review'
Good question . One poster above suggested they were becoming institutionalised on a 5 year cycle which could be worrying. These days replacement kit seems to run on a 10-20 year cycle of identify- design- build- service for anything substantial - in that time you could 3-4 reviews any of which may change the framework/strategy.
Perhaps the Civil Service like the routine - that way you can always have a core of people working on the next one whether it is needed or not.