Perfectly Ok to freeze thaw from -20C multiple times
Problem with denaturation and freeze thawing are usually linked to proteins so for a PCR mix consisting of small molecules like salts this is completely normal: so your mix should be stable for at least 1 year with multiple rounds of freeze thawing
Thank you for your reply. I was storing it at 4 degree as suggested in the protocol that we can use it for a month storing at 4 degree. Will it be a problem?. Now its been a month so i have kept in -20.