Yes, many do of the better ones are metal based. But as you noted, some are carbon based, including the highly rated Artic MX 4. Many also are ceramic based, like the popular Noctua NT-H1. Interestingly, the new HT-H2 is metal oxide based.
Of course the "issue" (if you want to call it that) with many of the metallic ones is they may also be excellent conductors of electricity. But as I noted above, that "issue" is mostly marketing hype from the non-metallic promoters.
I'm an Arctic Silver fan from way back when it was still AS3. I did some testing of good ol' AS5 a couple years ago and it still works pretty darn good. But, it's slipped down a few notches with better thermal paste available nowadays. I tried several brands and settled on Arctic MX-4 (no affiliation with Arctic Silver despite the "Arctic" in the name). MX-4 is non-conductive and mostly carbon based I think. It's also readily available and not too expensive. There are some other brands that are just as good if not slightly better. I still use AS5 on non-overclocked computers, since I have a sizable stockpile of it.
AS5 has to be replaced every some period of time (don't remember, a year or two) or it dries and simply starts to perform worse. It also has a curing period. MX-4 has full performance after applying and doesn't have to be replaced in a much longer time. MX-4 also performs better.
You can also find some other good options at a similar price and most of them will be better than AS5. Some are easier and some are harder to apply and this is also important.
Personally, I wouldn't buy a Zotac graphics card. There are brands which are offering higher quality or at least a better/longer warranty. EVGA is the best option if you care about the warranty. No idea what about the cooler on Zotac RTX2080 AMP but all their 2060/2070 had bad reviews because of issues with coolers. Or no 0 RPM mode or too noisy and perform worse than stock Nvidia cooler.
No it doesn't. It seems you overlooked earlier threads - specifically #17 above.
If you can show us ANY TIM, CPU, GPU, cooler, computer, or motherboard maker, or any whitepaper that reports TIM must be replaced periodically, I would be very interested in reading it.
I'll say it again - if you "need" the "few" degrees a fresh application of TIM might provide to keep from crossing over thermal protection thresholds, then you have greater problems you need to deal with besides your TIM being a couple years old.
Your temps should already be well within the normal operating temperature range such that a few degrees of degradation does not put you at risk of getting near those thresholds.
It is important to remember it is the case's responsibility to provide a sufficient flow of cool air through the case for the components inside. The CPU cooler need only toss the CPUs heat into that air flow. And it is the user's responsibility to ensure the case cooling is properly configured to provide that proper flow.
As for curing times, that does not bother me a bit for several reasons. The two main are (1), curing typically only gives you a "few" degrees better cooling. So again, if you "need" those "few" degrees, you have greater problems to deal with first, like ensuring your fans are spinning, you are not blocking air flow (good cable management) , or you have equipped the case with enough fans and they are all blowing in the correct direction.
(2) While time is a factor in curing, so is the number of heat-up/cool-down cycles the TIM goes through. And, at least on new builds, there typically are several before hard-core, extra demanding tasks, like gaming, are performed.
Gentlemen, we are bickering over the minutia here and none of it is assisting the OP with his build. Can we move this to the cooling section? I'm sure there are 50 threads over there arguing over the best TIM/application procedure/importance of curing/etc...