Well what you showed was wrong, it wasn't a way. I doubt any mines are operating 365 days a year also. You could do (30k*12+150k*3)/15 = 54k tpd more. Although as it is intial mine life and the tonnage could be increased by 50% to 100% for year 13 one can really only apply the 30k tpd higher for the 12 years. The rest is unknown.

Argueably if the drop results in a quicker payback period (you know having debt payments for not as long) and afterwards the tonnage is ramped up slowly through the cashflow the profits could be larger (you know that is the whole point of optimization). So I ask you, is it actually possible to raise our price? Just because the intial plan is for 12 years doesn't mean the rest gets zero value.