In my limited experience hotness is a combination of genetics and environmental conditions, if you start with good seeds ( Purira and Habanero are my favorites ) and try to provide the best conditions ( extreme Sun exposure, good food, moisture deprivation, root binding, ect. ) you will still find that individual plants ( of the same genetic makeup ) will vary in hotness - while I believe that the search for heat is secondary to the search for flavor , it is still the satisfaction of producing my own high ( endorphin stimulation ) that drives me after 25+ years of growing plants. Bill , escapee from nixon`s list , 12 year cancer survivor , highest ( 8540 feet ) chile farmer in Colorado.