How often is the Shanghai verification code updated?

The verification code library will be changed at the last moment of the card auction, and a batch will be updated every month, which is different from the verification codes in the landing stage and the first bidding stage. Basically, the replacement is started at the last minute, and sometimes it is even delayed to about 1 1:29:20 seconds. We can pay the price in advance to read the verification code. Brother Shanghai suggested not to cancel the verification code and pay the price directly.