If 4-5 year old paper had been stored at freezer temperatures I would trust it but if it has been stored at "ambient" temperatures which I presume you mean room temperature I would not.

I suggest you just try making some prints with negs you have printed before and compare color quality. In my case the paper was quite cream color for whatever reason and my thinking is that there was crossover, but in your case may not be as severe.

RPC