it depends . type of paper, how it has been stored are the most common question asked for buying old papers. For example some of the Agfa papers do not keep well at all, while kodak's azo may be good after 20 years.
The best method would be to take a piece of the paper in question and run it through the process, developer, stop bath and fix and then see if it is fogged. A small amount of fogging can be corrected, more may find the paper useful when one needs to pre-flash, and then of course some folks take older papers and fix them out for other processes.
It would be helpful to know which paper your talking about.