How long can mango concentrate be kept in a cold room before spoilage?
You'll need to ask your supplier - it's their product.
In general freezing will provide the best microbiological durability and give the best protection for most of the organoleptic attributes, but with Mango you need to be careful as it can change the texture - you'll potentially get clumping of the insoluble pulp, and it can be very hard to undo this afterwards. Thawing of large drums can also be time-consuming.
As a general rule of thumb an opened life of around 3 days at 0-4C wouldn't be unreasonable for this type of product, but definitely ask your supplier!