Around 8 months. Never submerged or kept it wet for a long time. Only used it for 5, 6 times. The largest craze is about 0.2mm wide. The top surface is actually not that bad, except on one corner which has a big one in it.

Got it from the following link. Just contacted the seller, so far the seller only wants to provide a $10 discount, which is a joke.
https://www.aliexpress.com/item/1005003545270291.html

If not the craze, the stone is actually good.