Salmon takes up smoke so easily, I'm not surprised that yours came out well with only a couple of hours of smoke. It's all in the prep to build up the pellicle for the smoke to attach to.
cold smoked salmon. i still can't figure out how to get the wood chips to burn for more than 1.5 hours without my intervention. maybe i need a more powerful air pump... but the smoke is intense enough that i just left it over night and it was pretty good flavour.