Firstly, there is the standard usage of Optical drives. CD-ROM, DVDs, and even Blue-Ray disks/VCR are used to store your footage for long periods of time. The only issue with this is these methods has become obsolete. There is also the use of magnetic hard drives and flash drives. These include External hard drives,SD cards and USB memory sticks. It will have more storage space than the previous one. It can also easily keep footage for long periods, while not losing it in the process. Finally,the best option is cloud storage or offsite server. This is because it provides protection and encryption at the same time. Regarding how long it can store for, it really depends. Factors like resolution,bit rate, fps and storage space affects the duration. Generally it is stored from 30 up to 90 days.