Shelf Life on Fly Lines?

If a line is kept properly, without being used, a self deserving fly shop should have sold the line before having to worry about "shelf life".
 
If it is coiled, then you have a memory problem, which is usually caused by the core of the fly line.
 
Mono cores hold alot of memory in cold weather, therefore, stay away from them for trout and steelhead.
 
Braided cores work best for cool weather fishing. They stay supple and hold no memory. If it does have memory (which all fly lines do in cold weather), it is from the jacket. But it can be taken out by stretching the line.
 
The longevity of a fly line depends on the amount of use and care involved. In the spring and summer I fish 7 days a week, at least 2 hours per day, and practice my casting just as much. My lines usually get replaced every 1 1/2 months to 2 months for casting practice and fishing. The average angler should expect to get at least 1 season out of a line, 2 at the most (in GOOD condition). But there are always exceptions. 
 
 
Best,
Michael Foreman 

i'm on my 3rd year with my 444line. less expensive lines, i've found, are stiffer coiled coming out of the box than more supple lines. cortland 333 is much stiffer than 444. it doesn't hurt the line that i know of. like fisherboy says, coldness and storage has a lot to do with it. cleaning a line often will help the line last longer. every winter i unspool my fly lines and hang them along the basement ceiling, like a cloth line. oh, ya i fish regularly spring to fall, that's why i moved up here. ~dt

Drake,
 
The older model 555's with the hollow mono cores were absolutely horrendous. I'm not sure who ever thought of that, but they should be shot for thinking it would make a good trout line. 90° + weather is ok, but still handles very weird while casting.
 
You should check out the new 555 Dyna Tip. By far the best cold water line in regards to memory.
 
 
Best,
Michael Foreman

I had the same problem with a 5 DT  555 line.  I bought it on clearance and got what I paid for.  I did however buy another spool recently for 7 WF line and had no problems with the 555. 

You guys purchased the old model 555 lines. I feel bad for you...really bad. See my above post in reply to Drake's. The hollow mono core is useless for anything but tropical fishing. You should have returned it to Cortland and had it replaced with the new model!
 
 
Best,
Michael Foreman

I used mine twice and let it sit on an old reel that sees only action from friends who want to try fly fishing out.  They don't know the difference