I have taken on board the wise words of Oracleyoda especially...

I have taken on board the wise words of Oracleyoda especially the Analyst style formula of a rise for 10 years and then a decline which clearly spells the beginning of the end and on that basis forms the basis of a SP decline. That would assume that NST ceases to have the capacity for new reserves, which I would dispute. 

If we look at other sectors for comparison by relating prospects to a potential outcome in an ever-changing world scenario. 

Look at retail - prospects shaky at best but reinvention through technology is an option

Technology - a left field change in technology can totally wipe out some existing players - e.g. 5g vs existing cable infrastructure

Commercial real estate - under pressure from work anywhere technology

Existing vehicles - under threat - electric cars - self drive cars - pollution threat refer Paris etc

The point I am making is that there is very little that is not under threat.

On balance I would suggest that NST is very much on the lower risk side for future survivability and track record is a very good indicator of future potential. The skill displayed by NST management gives me heart that the company will survive and thrive for a long time yet. I would expect the SP to be 50% higher by 2021 in line with forecasts.