Of all the things, this is the least I'm worried about in the long term. Storing video is expensive and rarely makes sense for businesses beyond 30 days. I setup a 64 camera network for a client and 20TB of space stores about 15 days of footage. Sure, disk space is cheap but at over 1TB/day, 500TB/year would cost about $15k in just HDD and triple that if you want redundancy with proper maintenance. I'd find it hard to justify the ROI on everlasting storage unless the store's selling diamonds.
Even for a small mom and pop store with just 6-8 cams, it can be $2k/year just in cost of storage. Pretty sure they would rather spend that on inventory, marketing, or staffing.