The very best rillettes are a combination of fresh and smoked salmon or trout; this gives the spread a more interesting flavor. If you're lacking one or the other, it's no sin to buy some salmon or trout to make this recipe -- but most salmon and trout anglers I know have a ready supply of both fresh and smoked fish on hand.
Once made, pack the rillettes tightly into jars; try to get as many air pockets out as you can. Once packed, melt some butter over the top of the rillettes, cover and store in the fridge. It will keep for at least a week this way, and up to 2 weeks if you keep resealing the butter cap between each use. You can also freeze the finished rillettes for several months.