As someone who is looking to purchase a Heritage TruHybrid, I see their "heat life" marketing and a few things come to mind. I have no doubt that it is indeed a marketing ploy, but either way I've been pondering it.
They don't elaborate "useable heat", where it is measured, or what designates the beginning and end of said time frame. Based upon a few graphs of their "heat life", I will assume they begin at the start of a fire before any heat is actually being used to heat the space, and end when temps are 150F. Their "comfort zone" as listed on a graph found in the YT video link below, is between 150F and 550F for the soapstone.
Our intention is not to purchase a wood stove for primary heating. We burn propane that is extremely cheap as of this time, but would like to have the ability to burn a fire for comfort when home and to offset the high fuel costs and/or scarce fuel is another propane shortage comes about.
Hopefully here in a few weeks or so I will be able to provide some of my wisdom on the subject.