Pick up some of this:
CRC Mass Air Flow Sensor Cleaner, 11 oz. 05110: Advance Auto Parts
unplug connectors (squeeze to release and tug to disconnect), unscrew (careful not to drop screws), remove.
Spray 'em down as directed (multiple bursts -- note the hot wire is actually inside the metal shell). Shake dry. Wait about 10+ min to be sure all spray has evaporated if you wish, re-install, fire the car up. Definitely won't hurt and may very well help.
Differences all depend on how dirty -- they meter air based on air moving over a hotwire, so gunk accumulated over time can affect those voltage readings.
Were you having any issues (e.g., wonky idle) or just asking in terms of general maintenance?