Since a few days ago I noticed that some of my SS are just vanishing i haven't unlocked any cheapters recently because I don't have much time to read, but I'm still collecting SS daily and saw that i have less and less of them on each day.
SS are disappearing
It had expiration for free ones. Check here for more information.
I love to see this kind of thread appears every week 
SweetsTomato It’s because it’s BS and everyone expects it to be a bug.
Velixar yeah, I don't like this expired thing, hey it can't be transferred, why don't let them collect it?
It will be used to read webnovel story after all, can't be sold either.
So why don't just removed this expired thingy
If you click on the SS area of your profile you will open a page that will tell you haw many stones will expire and when. The free SS that webnovel gives out will only last for a set period of time and then will expire. SS purchased will not expire.