Explored the first few pages of the gambling board and I found some casinos that are older than 6 months.
Whether they are worth or not to be added on your list or not, it is your right to decide ofc.
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Hopefully I will remember to take a look at these the next time I decide to add new casinos to the collection. Thank you!
After taking a look at the Casino Guru thread you linked to and especially seeing the post from Jaroslav, a forum admin, I have changed my mind and will remove Thunderpick from my table. Thunderpick is no longer featured on Casino Guru, but the admin says they had a low safety rating and resolved almost no complaint.
I have also found the casino on AskGamblers and they have behaved similarly there. Out of the 10 complaints on AG, only one was resolved, the others were left unresolved. It seems like they don't really care.
Thanks!