You could in theroy get the longer time from this tank however with it being only 28" deep your not really going to want a 30" TSN powering downwards in the tank as your going to get water EVERYWHERE, TSN'S will often stick their noses into the bottom of the tank and try to power their way into their food at least this has been my experiance with them... ALL 7 of them do it
Personally i wouldn't expect him to be in there more than 2 yrs