This is what Mike told me so long ago about the NPI that Liard has. It appears they estimated it would take 10 years before the NPI kicks in.

The remaining 6.6% interest is held as a Net Profits
Interest by Liard Copper Mines Ltd. We calculate this NPI does not
participate in the project revenue until years 10/11 after production.
Thus, should Teck elect for a 75% earn back, then for the first 10 years
revenue is split 75%/25% between Teck and Copper Fox and subsequently
70.5 Teck and 23.35% Copper Fox.