If you really want a higher valuation you could lower the...

If you really want a higher valuation you could lower the discount rate to say 7.5% for a valuation of $1.20, or squeeze the last drop out of it and make it 5% for $1.38.
However miners are almost exclusively valued on a DCF basis and 10% is the most widely used parameter.
PE is fine with a large diversified miner with many projects and enough cash flow to sustain ongoing development and advance new projects in the pipeline, and has a long term proven track record.
What happens to your PE valuation in say year 7, 8, 9, or at last year 10, when the music finally stops?
Who will pay a PE value during year 10 for your shares when there is one last dividend and then production ceases?
Note the DCF is based on the years of production, so the value declines as the remaining years decline.
Still, this company holds great promise and an increase in production and mine life will see for upside along with the POS.