Shoneyboy's advice is good, but applies to natural hog or sheep casings used for breakfast links, brats, polish sausage, etc. This is why it's important to be as specific as possible when you ask a question. No offense intended for anybody, so please don't take any.
Golson's question (I think) referred to fibrous casings for summer sausage and such. These sausages are fully cooked in the smoker, because they are smoked to a higher internal temperature, so they would not be cooked again. Nothing wrong with heating up a few slices of summer sausage in the frying pan before making your sandwich though!
Princess has a good suggestion about using wire zip ties to close and color code your fibrous casings if you're doing more than one kind. I have an automatic hog ring stapler, so I accomplish the same thing by putting different numbers of hog rings on the end and keeping clear, mahogany, and printed casings all on hand.
You can gain a little usable hanging length in your smoker by retying the original string loops smaller, or replacing the original dowels in your smoker with larger diameter ones. Both will result in your casings hanging slightly higher, but the extra inch or so you gain may not be worth the bother. You will still have plenty of headspace at the top for moisture to escape.