the buy back feature lasts for ages, Ive seen **** in there from weeks ago. or am I just trippin?

My brother has so much stuff of value that is larger than his bank slots and inventory. He wants to know if he were to sell his items to a vendor and then transfer his characters to another server, if his items will be able to be bought back from the vendor, once in the new server? And if there are any other methods to fix this situation. Any help is good help. p.s these items are too valuable to throw out