Your data saving ideas using certain definitions is very interesting and I will muse those options certainly. I like the FRAM idea and not losing the data after a restart. Know nothing about it but will investigate what is involved.
I am using DS18B20s (the real ones btw...lol) and the tank temps vary between 150 and 175 dgf so not a large span at all. And I currently am using straight integer values (no float precision) as my use of Stackstring for the webpage display precludes floating values. Which is one drawback about Stackstring.
Thanks for sharing your knowledge. 