Back in the late '90s, I remember hearing an NPR story on a bill for copyright extension. Disney was terribly worried that their rights over the earliest Mickeys Mouse would be lost, so they were lobbying hard to extend. It went from 75 years to 99, and the great grandchildren of John Phillip Sousa breathed a huge sigh of relief than they would get to keep drawing royalties.
Patent, by contrast, is 17 years (last I heard) but there seems to be a way to buy a second term. If ARM were to allow the 64-bit patent to lapse, that would be in something like 6 years – which could be a reason Apple has not implemented SVE/SVE2.
Personally, I was pretty pissed off about that jpeg patent that someone found in the bottom drawer of a file cabinet from a company they had just bought. I think the law should require a patent/copyright holder to actively defend their IP or lose it outrightif they just let it run off-leash.
Patent is actually 20 years, but from the effective filing date. (At least for utility patents, as opposed to design patents. Utility patents are where most of the action is at).
The 17 years was the old rule from the date of issue (it can take several years or more for a patent to go from filed to issued), but that rule is no longer the case. (In between there was a period where the patent holder could choose between 17 or 20, whichever resulted in the later date). The 17 years rule was before my time.
There is no second term on patents (and you need to pay maintenance fees along the way, otherwise the patent becomes abandoned).
As for your last point, there are some requirements that help. First, there is a sort of statute of limitations - you can only get damages for the previous six years. And there is an equitable principle called laches, that means if you know of infringement and do nothing, you could conceivably lose the ability to sue, at least on that infringement. (Though this principle is much weaker due to recent case law).