Ah, compared to the historical methods used in UrW the modern method that I'm using is more like cheating =) The way I do it takes about 45 - 60 minutes, and if I understand the underlying physics correctly the fish is actually boiled because of the vaporized moisture inside the container. So this modern way is mostly just a way of cooking the fish, giving it a nice aroma of smoke. I'd guess it would last maximum one week in a fridge.

But the method in UnReal World simulates so called "cold-smoking", when smoke is maintained for a longer period, always keeping guard that the temperature is not too high nor too low. And that doesn't happen inside a closed metal container, so all the moisture just slowly vaporizes away, the smoke kills all the bacteria, and seeps into the pores of the food prepared. That takes a lot longer, but is actually a way to preserve food.