My experiences with NH is that sometimes space appears 2 months out, sometimes 2 weeks out
Equally important, as noted above, find creative routings. I wouldn't expect too much inventory to/from YVR on NH. I've seen the odd spot. But there always seems to be space from IAD (not my first choice) ORD, sometimes SEA and I've seen SJC and rarely SFO. And my searches are really random.
I've done NH F LAX-NRT, NH F NRT-SFO, a couple of regional Asia/SE Asia NH J as part of a larger trip.
I found this 10 days out and booked it. AC to ORD to start and AC from LAX to finish.
Another example: for the last 2 weeks or so, there was a lot of inventory LAX-NRT for July 22 in both J and F and on both of the daily flights.