If I had to guess, I'd say two weeks (12/23-27/85, 12/30/85-1/3/86). Thus, S-165 aired 12/20/85, S-166 aired 1/6/86. No inside knowledge--just a shot in the dark.
That'd make sense, except that Season 2 started on September 16, 1985 (and per a couple of uploads on YouTube, Alan Cevednik's eighth game aired Thanksgiving Day), which puts #S-165 at 12/13/85.
The closest thing I can find to an answer is
this recollection by an audience member on ATGS back in 1999. Per said poster, Rocky's last two shows were taped in December '85 and aired in early '86.