Log retention & monthly uniques

In briefing large third parties about the policy, we've encountered a range of feedback about the 7 day log retention period. One opinion was "7 days is exactly enough; it ensures we'll have business days to deal with a problem, even during a holiday". Another opinion was "10 days would be much better". A third opinion was "31 days is a magic number, it lets us get a good handle on monthly unique visitors".

We should pick one of these for the next revision.