Lifecycle of cabling?
 

What is the expected lifespan of aftermarket ICs and power cables? Are there any general guidelines?

As long as you keep them dry and they don't oxidize, I would say indefinitely. I have a couple pairs of Synergistic Research interconnects that I bough in the early 1990's. They still pretty much look and sound the same as when I bought them. On balanced cables I would be careful not to put that much stress on the XLR fitting. I had a set of ARC cables I had to have re-terminated because the wires came loose. The ARC cables were fairly thick and heavy. I now put little supports under the wire ends of my balanced cables.

What I do in my car audio installs for my oun cars is this. I’ve tested it with a few on my porch and garage audio systems and it works great
I’m a master mechanic by trade and there is a jell type material that’s called dialectic grease
you put it on all your connectors and then you install them like you would normally
This stuff does not interfere with any of the current or signal going through that connector
So on an RCA cable you could put a little dab of the dialectic grease on the RCA cable and plug it into the Jack and that will make a water tight and atmospheric tight connection so that there will be no oxidation or moisture penetration getting into the plug

Automotive dielectric grease is good in the harsh automotive environment. But for audio cables, if a anti corrosive element is desired, I would suggest Caig Labs Deoxit Shield S100L. The green Deoxit bottle. It provides a protective barrier.
The three main Caig labs products: The Gold for normal cleaning of relatively clean conductors, and protective finish. The Red, for better cleaning, to be followed by the Gold. And the Green, to form a protective barrier in harsher environments. For my personal cleaning of new dirty' wires (like on low 1 or 2 ohm impedance, but large body resistors like Duelund Cast, I use Meguiars Scratch X automotive polish. It really takes off the tarnish wonderfully, then I use the Caig Red, then Gold
The main problem with Automotive dielectric grease is the Human contact, particularly getting it on hands, then eyes. Dielectric grease is rather dangerous to eyes. And if it is on your hands... It will get in your eyes soon enough.

I have used Dielelctric grease for small quartz crystals in Audio RFI applications. and would say dielectric grease is a 'difficult' product and extreme care needs to be taken in handling it. Mainly for the immediate effect it can have on eye irritation. and that if it is laying around, later failure to take precautions about eye contact.
If you ever do get it in your eye, then you WILL remember next time ... It really hurts.

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As far as cable longevity.. I own cables I made back in the early 1980's and aside from replacing the old cheap 'gold' Radio Shack RCA with high quality "Tiffany' style Vampire RCA, they are still fine. Same for some OFC wire from late 80's. The one wire which has problems is silver plated copper, bare ends used for speaker wire does tarnish to black in a few years where exposed. And bare copper also tarnishes is used as bare wire in speaker applications.
Best to just cut off the ends and refashion. Those wires certainly could benefit from an anticorrosive protective barrier like automotive dielectric grease (with the caveats about eye contact even years later) or the 'Green' Caig Labs product. For RCA plugs etc, kepeping a seal so fresh air cannot circulate really slows any oxidation. LIke in AC plugs, if the rubber seal at the end is tight, the wires just stay fresh, if the plug end is open they tarnish a lot more.
For audiophile 'quality, also the copper wires connecting the AC duplex in the wall, tend to tarnish over years, and are typically neglected. Plus they tend to get loose physically sometimes. Good to check up on them every few years.