Does anyone have any idea how many years gel spun stays good for? I know that monofilament is usually bad after a couple of years, but I'm wondering how frequently I need to replace the backing.
I don't know but I think An Ren at Patrick's may.
Sorry I'm a little slow on this one. Any type of line, Dacron, spectra, Dyneema are pretty darn long lasting. The one enemy of any line is UV. So unless you're spooled on a very regular basis and you leave it out there in sun for a long time, I wouldn't worry about many years of service. Now if we lived on the gulf coast and your reel was out in the sun many hours each week, I don't think there is a problem. As an example I deployed data gathering equipment in the ocean for 3 to 7 years. They were held in place with anchors and floats with spectra line in between. When they we recovered them, the lines were sent to a lab and tested for strength and it was found they had lost less than 10% of breaking strength.
Hope that helps.