Good Morning Ron,
I do have 127.725 in the scanner and I noticed the same thing. Actually, I realized it some time ago, before I put the feed up, that I was hearing the controller but no aircraft. Like you said, this was occurring later in the evening, typically after 22:00 local time. I did some searching and found the aircraft on 127.725. I do believe the controller is broadcasting from Williamsport, although I can't confirm, as I hear ZNY fairly strong on the scanner in truck when I leave work, but as I travel further west towards home, they fade out. However, ZNY normally simulcasts on 128.575, 132.15, 123.62, and 134.8 when conversing with these later evening flights, again typically after 22:00. So as long as I keep 127.725 in the lineup (with no delay activated) you should hear both sides of these late night flights, with the controller answering on either 128.575 or 132.15. I really can't say for sure if my dedicated aircraft scanner for the feed is receiving 127.725, because I'm usually heading off to bed about that time and just haven't checked.