I think that the method of smoking would be a factor in shelf life of smoked fish. I cold smoke salmon and trout for about 40 to 60 hours and make a point to keep temp. down to 100 to 110 degrees. I know others who smoke fish at a higher temp. for shorter times and keep more moisture in fish. This is a "wet" smoke with a much greater need for cold temps and has a MUCH shorter shelf life(weeks intead of months). A lot of the process I use is slowly removing most of the water from the fish. I use honey instead of sugar and remove skins prior to brining, the skin generates slime that makes it a requirement to rinse salmon after brining to remove taste and bacteria. By not using skins the honey and spices are retained more effectivly then by rinsing and overall flavor is improved greatly.I also remove most of grey fat under skin, I think it improves taste to do this. A little more work to keep fish from sticking to racks, the upside is that after 24 hours I flip racks 180 degrees using a second rack on top and oils stay in the fish throughout it.The lower temp. and use of honey instead of sugar are related in that the honey acts as a preservative in its' own right so long as it isn't heated above 160 degrees, making less salt possible.You can see the red oils come out when I vacuum it, omega 3 oils are not destroyed by high heat in this method. I can send salmon vacuum packed in the mail, safe for two or three days, but I overnight it to make sure. My salmon can be left on the counter at room temp for 24 hours and it dries out a little, kind of turns a little more like jerky, but certainly not evn beginning to be suspect. I've had folks carry my salmon around in their pocket all day while they did chores around their farm, and I know some hunters who also use it unrefrigerated for days at a time. Voltage regulators on big chief smokers helps with temp. control. If fish are not frozen first shelf life seems to improve as well.I have a shelf life refrigerated of 6 months to a year.I chunk all fish (except smaller trout, kokanee or jacks) rather then whole fillets,I leave skin on the trout and smaller fish, but scale fish before brining (another source of bacteria and off taste). I know there are other methods, I've developed this way of doing it after 34 years and lots of input from others, both native american and scandinavian.Interesting read on shelf life.Sorry for your loss, I know how much work it is to smoke 50 lbs. Thanks for post. Bob R