how long does cex or a pawn shop buy/sell/trade sort of shop keep their cctv for before getting deleted?

That seems like an odd request. You'll have to contact the store to find out.
Different stores / companies may have different policies on the length of time to keep videos.

As long as possible.

Why do you ask? Are you planning a robbery or something?

LOL, or sold something that didn't exactly belong to you?

It's confidential information and to ask is to look suspicious.
Ig I asked you what times of day there is nobody home at your house would you answer? I don't think so...
But then, why would anyone want to know this......

Well, from the other side of the coin, maybe someone pawned something that was stolen from the OP, and the store is telling him they don't have video of it...?

In any case, the answer is the same: it depends on too many different factors for anyone here to give a definitive answer.

Perhaps the OP should call the shop in question and ask them..

Oh in that case we should tell him / her everyone's confidential information without further enquiry.

it all depends on how old the system is. if latest h.264 compression then im sure recording can last for weeks at least.

Most retail establishments I have dealt with try to keep two months of video on hand (department stores and such). Your common gas station is normally about a month or so. Never installed a system in a pawn shop, but I would venture to say at least a month.