So far I have one verified gambling account only which is my Stake's account, it was not a long process since my account was verified within few hours only.
Of course the speed of the verification process will be depending on some factors, the most crucial one is the human resources on the platform who are in charge to do the verification process.
The more staffs (both in number and experience) who is handling it = the faster verification process IMO.
I have not done other KYC in other casinos so I have no idea about average speed, but I have to agree that such verification process should not be done in more than 3 working days.
Trusted casino will verify your KYC very quickly provided you have provided correct and true documents. There is no point for the casino to deny the KYC if there is no fault. Why would casino deny anyone genuine KYC and not let them play.
However, there are some scam casino who will use KYC as a tool to deny our payments. They will allow us to deposit without KYC but when it comes to withdraw they may ask for KYC and if the amount is big, they may deny the KYC without any reasons.
There are cases that it will be denied if the picture of your ID is blur or each side has not been presented well. But other cases than that if everything has been fulfilled then I guess there's no point for casino to denied your KYC verification. I can only see this happening to those site which do delaying tactics so that what people request especially withdrawal will take time or just denied the withdrawal made by that person.
Trusted casino didn't do any further more issues if they see that all documents has been presented well that's why its good to choose reputable casino so that we can avoid any problems regarding on this matter.