Sorry for the late update, been busy with IRL stuff.
The fibers regrow very quickly, dont even take a night. At the start of the game, you are told to pluck fiber and is used in alot of things like making tools, building and of course, the excess can be use for fire.

Oh, I did think of fire might spread in case of a forest fire going, I have seen live streams of campfires burning down the base. Which is why i chose to build the campfire close to the capsule transport which landed us on the planet, since Its metal.

You can get seeds from fiber and when you combine fiber seeds with berry seeds you get a fiber fruit bar which in my opinion is one of the best early food you can get in the game, I feel even making Jerkies dont last as long as the bar which is great for exploration early.

As such, i tend to have a habit of running forward and consistently spamming the interact key to pluck fibers. Its almost a 1st reaction when i see the fiber on fire that i rush to pluck it up. I glad it worked and the effect of getting caught of fire didnt cause too much damage to my health. I dont think I know how to put the fire out of me if I really caught on fire for too long. The lake is some distance away. I may had died to fire if thats the case. xD

I hope your holidays are going good for you or your preparations are. Cheers~