Re: Cracked Fly Line
I have found that every line I have ever owned with an epoxied braided loop on the front eventually became hinged at the point where the braided loop material ends. I also found that on lines 4wt and under the braided loop on the end of the front taper seemed too big & heavy for the light lines. I switched all lines to a nail knot butt years ago. If you use them enough your line will hinge at the nail knot sooner or later too.
As far as a line that becomes surface checked with age; I still have the first SA 5wt in gray finish that I ever bought, it is checked from end to end and I use it for streamer fishing. The checked surface does not affect the performance of the line in casting and I just hit it with a little Mucillin now and then for better mending. Don't toss those old lines out, you can dye them and use them for wet fly fishing. Yes, I said dye them..........