Buccal swabs can be stored for up to 5 to 7 days at temperatures between
15 degree C and 25 degree C.
I would recommend storing buccal swabs at 4 degree C for a maximum of
2 weeks before processing if you need to extract DNA without any loss in DNA yield and quality. If unprocessed buccal swabs are stored at room temperature, bacteria and nucleases present in the swabs can cause DNA degradation.