I have never seen this info published, but I would not cut it that close.

At LAX they officially close the counter at T-45. I showed up once at T-65 (delayed inbound) and the checkin desks were almost empty. One TA, One manager and one other person. Had no bags, so do not know if that would have been an issue.

But what if a family and one other showed up just before me and delayed me 10 minutes (very possible when down to one queue)? Might have been bad.

That is with LAX with a nominal T-45 close, YYX and a few others are T-60.

If it was me, I would assume I need to be there by T-90.