Exactly what I was thinking as I was browsing this thread. If I can understand the code by visiting as few files as possible and reading as few lines as possible and not having worry about finding those, job done.

There should be a metric that indicates aggregate LoB for a codebase. Simplistically, cluster references of all entities (variables, functions etc depending on the language), calculate the overlap of those clusters and aggregate them. Track this metric over time and when it breaches a certain threshold, refactor until it’s back to where you want it to be.