Certainly, I think you're correct that some proponents, and there are strong proponents of the mineral exploration tax credit, favour extending it for further years.
I think it has always been analyzed in a particular context. While the proponents are certainly in favour of the extension and of making it permanent or for multiple years, generally it is one of several factors that go into the exploration decision. Exploration may be driven by the prices for metals as well as by tax incentives. If prices for metals increase a great deal, then there's an argument that the particular incentive is not strictly necessary. There's an assessment each year as to whether its continuation is appropriate.