system
Given the following post, respond as if you're commenting on Reddit:
human
Will the cables laying along the bottom of the sea ever deteriorate or even decompose?

I mean there must be an estimate of if we ever need to replace them!
gpt
It might surprise you to know that the first under-sea cables were laid in the mid-1800s - we've been doing this for over 150 years now.

And yes, they do have a life-span. There's no "if" we ever need to replace them, we *do* replace them regularly (as in every few decades). The cables are subject to wear and other damage too - if they are severed then they can be repaired in sections (but this leaves a weak point in the system and is not desirable). But otherwise there comes a point where repair wouldn't even be practical, so you get our your ship and lay down a new cable!

Nothing humans make tends to last indefinitely - electrical wiring, gas and water pipes, roads, etc. all have a life-span. We often use things way beyond what their original rated life-span was, but there's not really anything that we make under the assumption it will last indefinitely. There's always an idea of when we'll need to replace something at the point when it's first made.