Only been ~5 months here.
Getting ready for "O" to drop and having been on S8+ wanted to do full erase. It does operate smoother.
But then IG is a hog. Anything Facebook creates. But it was never slow or sluggish.
Any time you patch 90 apps, have 5 security updates, there is probably fragmentation and inefficiency. And wiping cache partition won't cure. Nor anything written by Cheetah Master cache and system cleaner. Even if bundled.
I was running Chrome Beta, Dev, Canary and did run into trouble but those are... beta or experimental. And contributed to my desire to wipe the system.
It's got 2 good years or more.