We aren't really given the complete lifecycle of the Gw'oth. But the explanation given in the wiki is a bit of a misnomer. The time period mentioned for the Gw'oth going from discovering fire to mastering nuclear fusion was just under 200 Earth years.
This time period would have been maybe three generations in human years, two if the humans lived an exceptionally long time. The period they would be using was in human years not necessarily Gw'oth years. The conversation where this is revealed is discussing just how fast and the method the Gw'oth use to develop their new technology.
Nessus said, "The Gw'oth broke through the ice of their ancestral ocean less than two Earth centuries ago. Before that, their technology was stone tools. Now they have fusion and hyperdrive."
"Two centuries," Louis echoed.
--Betrayer of Worlds, Larry Niven, Edward M. Lerner, page 48
The Gw'oth increase their cognitive abilities by forming group consciousness through the merger of their physical forms in essence, becoming very powerful organic supercomputers. This capacity is so great that when a group were taken prisoner, they were able to form a unit with eight members who were capable of inventing hyperspace technology independently just from observing that it was possible while on board a Puppeteer ship. They went one step further and created their own drive while cannibalizing the parts from the Puppeteer ship holding them prisoner and escaped from custody!
An art exhibit displaying a Gw'otesht (a large collection of Gw'oth) with their creator Edward M. Lerner.
A description of the Gw'oth from "Destroyer of Worlds:" A Gw'o (singular) had five limbs arrayed about a central disc, sort of like a starfish. Spines covered the skin, again like a starfish. There the resemblance ended. A Gw'o's skin changed colors like a squid or octopus. Its appendages were flexible, like those of an octopus, and hollow like tubeworms. Tier after tier of sharp teeth ringed the inner surface of each tube. Eyes and other as-yet unidentified sensors peeked out from behind the teeth. Almost certainly Gw'oth had evolved from some type of symbiotic carnivorous worm colony.
Just a note: Some tubeworms on Earth are impressive organisms with very long lifespans. Lamellibrachia luymesi, the tube worms that live at deep sea cold seeps and grow very slowly for most of their lives. It takes from 170 to 250 years for Lamellibrachia luymesi to grow 2 meters in length, and even longer worms have been discovered. (The Gw'oth also inhabit a home world with a very cold ocean and they lived at great depths much like these worms do.)