I am somewhat surprised by the comments here. In most industries, self-regulation by a recognised industry body is usually regarded as a good thing - it helps keep down the cost to the taxpayer funded national authorities, and also discourages (not prevents) some of the worst excesses of behaviour. Inspections from the likes of the CAA, FAA and others certainly have their place - but there is no harm in the odd bit of self-policing.
In theory, a company that passed an audit last year and is well run, should not need to prep for an audit the following year. However, if you had to retake your driving test every 5 years, could you be certain that you haven't picked up any minor bad habits and resist the temptation to have a glance through the Highway code the night before ?