I have in mind three, maybe four, 20-page articles that could be of value to weightlifters/bodybuilders. These would present uncommon, possibly even unique, methods for achieving certain ends, learned in over 20+ years practicing those hobbies. They would also have a very long "shelf-life", and can stand on their own merit. So I have no intention of giving them away. After those I don't see foresee writing anymore articles in that niche.
I sit towards the over-delivery end of the spectrum, so I'm not going to crank out 20 pages in an hour, not even the first draft! I estimate the first article will probably take me closer to 30 hours to complete.
Would you just "go for it" and spend 30 hours on the first article of this potential series and put it up for sale, based on your gut feeling? Or would you do some testing before you write a word?