How significantly does a new piano change tone over time?

[Timtin]

Thank you Alfor for the link. The device they offer seems
to be not unlike my duster on one end of a ruler. Maybe I
could refine this method by using a sock instead, fitted over
one end of a flexible straight edge of the type stationers sell.
Having said that, Brian's leaf blower idea still looks to be the
efficient in terms of speed and how searching it is.