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.
Loon