I'm on the same boat here with Centurylink fiber. They rolled out fiber a couple years ago for $170/ month and I that price point i knew it would not be worth the cost with our household usage. I got 40mb fiber instead and even in a fully streaming household it held up with no problems.
A couple months ago centurylink dropped the gig price to $85/month lifetime guaranteed price. I said what the hell and got it but boy am I underwhelmed. At first I was getting 850/950, then 700/950. It took some tweaking and swapping switches to finally get 950/950. But even then most downloads are still just 3-4MB/s, same as with the 40mb/s plan. The fastest it's done was android studio at 100MB/s but that's it, nothing else has come close. I uploaded ~20gigs of video to youtube and it maxed out at 140mb/s. Hard to tell where the slow down occurs, I wouldn't be surprised if centurylink was throttling because I know they throttle netflix.