I use Orvis knotted leaders, as well as other brands and those I make myself. I always use Orvis SS tippets (unless I am fishing flies that twist tippets, like fanwings, then I use Maxima).

Here are some Orvis leaders from the early 70's. They are as good as new. I use leaders such as these but do cut the tippet off the knotless because the extrusion machines tended to leave lumps every six inches in the fine nylon. I haven't bought a new leader in twelve years.