I think if you are talking about bimacs, although they can survive at room temperature( above 70 deg F), they will thrive at their native and natural temperature range of 54-68. Clearly there is a lifespan range, and the experts feel their average lifespan is one year. In my limited experience, I have not been able to identify the factors leading to growth and size variations and time to senesence and death when I controlled for variables like food availability and temperatures. I would be interested in tracking all of my 100 octopuses, 70 of which have been sent around the country. I know some have already died-they would be 10.5 months old now. Personally I keep my aquariums cool with chillers. Currently, one tank is at 57F with 6 in it; 3 others are set at 65F with about 10, 5, and 5 bimacs; the smallest tank is 125 gallons. Colder gives you an advantage not only in relative life expectancy because of the metabolism but also gives you a little wiggle room for human errors as in water quality issues. We will keep everybody abreast of life span as the captive raised bimacs reach the end of the lives. No eggs yet but I am hopeful and I feel they (the females) have mated- if only it was easy to tell them apart. For those of you coming late to this website I would refer you to the June 2006 TFH article I wrote about captive raising of my bimacs. Zyan