Right, I also thought I could work around the issues by ignoring fluctuations in the data. The problem is knowing what is the correct baseline data. In your example, the education:concentration might be missing when you first start checking and only start appearing a long time later. Do you ignore the data when it first appears or report that the person just added another major at college (which may be true!)? This is a bigger problem with fields that people might completely add/remove instead of simply updating (e.g. relationship status). I tried baking in a time period (e.g. 24 hours) in which I ignored all changes and waited for the baseline data to become obvious, but even that didn't work because some data took even longer to re-appear. At some point I had to admit to myself that - with all these work-arounds - my simple feature had turned into a hack.