he should play as few as he needs to in order to keep healthy and manage his injuries.
tennis needs him on tour for a few more years, we already lost Roddick. Hewitt is still playing, Rafa should be able to if he is smart about his health.
still, it would be good to see him at Wimbledon, US open and WTF this year (and Aussie Open next year).
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM