I don't actually know much in detail about core analysis, but one thing I have learnt from experience us that there is a fairly well developed relationship between the time spent on a drilling programme, and the appearance of credible results.
Doesn't matter whether it's oil, gas, coal, gold, tin or any other damn thing, if there isn't a credible reserve body within two years work, or one year's work if you are following the Old Man, there isn't one full stop.
The crucial exceptions are when you are either developing a completely new technology - the fracking boom is a good example, because the existence of the reserves was well known, it was the extraction techniques that needed developing - or when the whole geo-political situation causes a radical change in the economics, as happened in oil in the early 1970s leading to the great North Sea oil rush
plus ca change, plus c'est le meme chose