Well not only he is already 38, he has also already made 1198 appearances in his career, the most out of all outfield players in football history. Sure his legs are long gone considering the number of games he has played and his age. He is not a super human afterall.
I don't know what more he wants, he will never win a WC or Ballon D'or ever again, there's nothing else he could added to his cabinet, and there's no records out there for him to break anymore. Besides, Saudi Arabia trophies are all worthless/irrelevant anyway, nobody cares if he wins anything or nothing there.
Maybe he should just try to play for fun, try to be less competitive but enjoy every moment on the field instead, not caring the result just like most retiring players in lesser league, and happily collect all his oil money at Saudi Arabia until end of his contract, and then call it a day. The moment he choose Saudi over our bench, he should know where he is heading to.