Dz told me to come here so ok-
It could be different/random for everyone, but like Dz said it could’ve been changed at a certain time so people who got their Emerald ranks after whenever the length of the exp booster lasts was changed actually lasts for a longer period of time. woah I worded that weirdly- pls tell me if you would like me to make that clearer
I got my Emerald rank in December 2018 and my booster is gone (probably lasted around 1-3 months or so); I also have other friends who got their ranks between 2016-2019 and their boosters didn’t last long either. Honestly I never knew the boosters may have changed until I started hearing from people who got their Emerald rank recently (around mid-2020 to today) ended up keeping their boosters for a longer period of time than those who had their Emerald rank for over 2 years or so. Though, if anyone has lost their exp booster and gotten their rank during mid-2020 and today, then it could be random, although idk anyone who has lost their exp booster.
If your exp booster is gone, you could tell by whether or not the chat is telling you if your coins and stuff are being boosted or not. Although, apparently the boosters from gems could be working if you still would like a boost- I was getting 4.5k exp from 1st place in kk once and I opened a gem booster and ended up getting 9k from first place the next round. I don’t guarantee them to work though; it’s obvious to tell whether or not it’s working in kk but it’s hard in other games.
I hope this helps :)