Thanks for the tips, Dendawg and Steve. I am very familiar with the Esposito and Clarke trails, including the spur that goes to Blauvelt. I guess I thought I was going to take the Ash Street side-trip to Piermont and spend some time there, possibly pushing the four-hour time limit. However, after an hour and 40 minutes, I had been to Oak Tree Road and was back to my car in Tarrytown, having only stopped briefly to chat with some locals.
My sense of time sucks. This is why I always arrive an hour early to work and everywhere I go.