I remember on the Boeings that the air to ground reporting was not continuous, but at specific points throughout the flight. Trends were determined from one flight to another. However, if limits were exceeded, special air to ground reports were generated.
Vibrations do tend to jump about a bit even during normal ops, so trends would be hard to track. Also, some high vibration readings are due to faulty sensors/wiring, which probably won't show a trend.