Both times, went in mid-December.
The first hunt, I missed a billy about 43-44" inches at extreme yardage, which was the biggest I saw, never saw him again. Killed the next best billy out of the same group 4 days later on the same hunt, longest shot of my life. Probably saw 300 ibex total, of those about, about 30 billies. The ibex hunt was secondary to Marco Polo which I was the cameraman, so we spent 8 days focused on sheep and my hunt was never the primary focus. I'm very happy to have taken a billy.
The 2nd hunt, again, I was the camera guy and my hunter shot a 37" billy on day 1 of hunting as it was not the primary focus and he was not concerned with trophy quality, a representative mature billy was all he was interested in.
If ibex is the focus and export permits are available, I would go to Kazakhstan or Kyrgystan. The billies are bigger and the guides are more focused on getting quality ibex. Tajik ibes are usually just an add-on or what the observer shoots and the focus is almost always on the Marco Polo so the guides can squeeze you for the biggest possible tip for the sheep.