Hi Ruslan :
After 35-40 flights, I see very slight color discoloration. I copper wrap my ends and that area was the first to discolor- likely due to the natural oils and salts from sweat in our hands. That very same thing happens to the copper wrapped ends of my stainless and solid lines , so I'm not at all concerned about that.
I'm wiping my lines with a clean white sock lightly doused with Acetone. Seeing some dark brown from the brass. Going to next try a micro-fiber towel.
I was initially using "Goof Off" to clean them, but stopped. At first, I was wearing latex gloves because it's certainly harmful to our skin( to say nothing of our model finishes )to use such powerful chemicals. I Googled the dangers of skin contact with lacquer thinners, lighter fluid , gasoline and Acetone. As one would expect, they're all bad news and even though I've been handling this stuff for over 50 years, I'm more concerned about carcinogenics at this point in my life than ever before. Guess I want to hang in there some more for the sake of my children and grandchildren. Strangely enough, I discovered through research that traces of Acetone can be found in our bodies and if kept to a very minimum, we're ok. Any doctors out there , please tell me otherwise and I'll follow.
Back to the lines, I double wrap around the thimbles which is a little more tricky than stainless but doable.
I will definitely seal the ends prior to snipping with either CA+ , nail polish or some other clear product. I think that is extremely important ;not only for easier handling during preparation but to prevent wire fray at the thimble end where the last of the wire exits.
I continue to wipe them with a fine instrument oil after each session and store them in a paper lunch bag in the driest area of my home.
If anyone out their interprets some or all of this care and concern as a p.i.a. , well it sorta is but its well worth it and based on my current experiences, I won't hesitate to continue to use them with the expectation that they should be replaced once a year. They sure feel great. The brass/steel .016s I use may not be AMA legal at events like the NATS, but I keep a set of solids which have a similar feel should I ever decide to dip my toe again.
Glenview NAS '72 was a long, long time ago...