Thanks for your comment. So, the help file you linked says:
"Each geoprocessing tool that creates new output data or updates the input data will add metadata about the execution of the geoprocessing tool, which includes the tool name, its location, and the parameters used. This behavior can be disabled in desktop applications by un-checking the Log geoprocessing operations to a log file option found in the Geoprocessing > Geoprocessing Options dialog box. In a Python script, logging of geoprocessing history can be disabled using the SetLogHistory function.
Metadata for a dataset is viewed by right-clicking a dataset in the Catalog window or ArcCatalog and choosing Item Description."
You can see I do have that box checked in geoprocessing options:
I performed a test, a simple export of an FC to a shapefile, just now. Here is the item description window for the output, showing results only up to October of last year:
Do you see what I'm saying? I'm wondering if there is some kind of limit on the length of the geoprocessing history.