"I didn't make myself clear with the last point: Do your think 30 years
accumulation of dust on the lander parts left behind is enough to make an
accurate calculation of what there should be for 10,000 yrs vs. 4 billion
years?"
Probably not. If the moon were 4 billions years old, the rate of dust
accumulation would be expected to change, so whatever the rate is now, there
is no guarantee it has remained constant throughout its history.
Kevin L. O'Brien