Do not know where you get that 4-year period. My direct experience with QAN and NCM gave the 2-year basement building process. Suggested to my first son, buy half now and wait until Nov to buy the other half. Jan '18 is the two year anniversary from the low, but Oct and Nov could be the bottom for commodity. If one has a 3-5 year time-frame, it really does not matter to buy a few months earlier.
The two main factors that drove STO down are (1) oil price and (2) debt, IMHO. Both are now improving.
The above are just my observations. I am not an experienced investor and I am not trying to convince anyone in anyway.
STO Price at posting:
$3.85 Sentiment: Buy Disclosure: Held
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