I think this means different things to different people. Those system administrators who have worked for different customers are used to doing a full system audit when they enter the system. This is done to provide them with some perspective of what the instance is used for.,
After this though, “audit” to me, is linked to some action like “cleanup” or “correction” which can slow the actual audit.
Workfront produced a user group on the subject of “system maintenance” earlier this year where this is discussed with the perspective of how to make this easier by building your instance more simply. (you can search for it using those terms)
I think @Doug Den Hoed‚ over at AtAppstore also has dived very deeply into the subject of auditing as a means to discover how “healthy” your system is.