Having worked for a company that did refurb work I can tell you that it can be a crap shoot. In the case of the product that I worked on, a group of items were torn down, cleaned and tested. Come re-assembly time refurb items were built from the bins of cleaned tested parts. when a certain component bin was empty then a new part was used. Some items get nearly all new innards and others are mostly used components. The used components were tested for functionality but durability was anyone's guess. The ones with nearly all new components lasted as well as a new item, the ones with lots of used not so much. Ya pays your money and ya takes your chances, depends if you're a gambler or not I'd say.
