Well, first of all, it is your son who should be asking these kinds of questions, not you. Secondly, the answer actually depends on specific facts that only your son would know - what contributed to his not getting an offer, did any of the firms he interviewed with last year tell him to reapply the following year, what does his school's career services center suggest, etc. This issue should be solved by your son, not by you. Your involvement in his job search (beyond simply giving him advice) will do more harm than good.