One nice thing about flouro I find is when trout fishing on east coast with 5x and 6x tippet, the stiffness of the flouro makes leader repairs so much nicer than traditional mono. Oh and when bobber fishing you can get away with less weight to get the beadhead pheasant tail down. Fluro is much more expensive, but in some circumstances worth.
I had a friend who used to mark his spools and throw them out after a year. I just test it when I tie a knot and toss it if I get a couple of failures. Flouro is supposed to take a lot longer to break down so maybe that might make it a better deal?
We are hopefully entering winter here in the northeast and getting flies deep and fast will be a priority. This usually leads me to pick a narrow diameter line. But if steelhead are in the rivers I will go for higher strength since the heavier flies sink well by themselves. At the same time flexibility of the leader/tippet is important. As a habit I give the line a good stretch to get a good cast and drift. I find mono better for winter fishing. Any thoughts?