Haven't read it in full, but skimming, this seems useful. Lots of detail about the timing of Revere's ride.
http://allthingsliberty.com/2014/04/dissecting-the-timeline-of-paul-reveres-ride/
Thx for finding this. I look forward to his book.
Beck says PR was in Lexington for a total time of about an hour before both PR and Dawes rode off.
OTOH, Fischer states his opinion, without quotes or a footnote, leading the reader to believe
total time was about an hour and a half. See p.110.Fischer.