We keep our fish at 84-88. Average temp is kept at 86. I have found that lower than 82 and you are asking for trouble such as internal parisites etc. We have always kept the temp at this 86 range and have fish that are 12 years old, so I don't know about the live shortening aspect. In other species of fish that are not genetically fit for the higher temps it will definitely shorten there lives. Also the higher temp really encourages growth... I have had numerous guest to our facilities as of late and they all have said they can't believe how big most of our fish are. Adults usually end up in the 7-8+ inch size.