I don't know, as many as he can, I guess. If he can stay injury free, his physio, who knows his body best after Nole himself, predicts Nole can play on top level for another 3-5 years. Since it is getting harder and harder to play physically, this will be the main thing with Nole. So planning tournaments and rest/downtime will be crucial.
Also having a bit of luck in schedule and draws. He is one of the rare players that goes very deep in almost every tournament that he plays (semis and finals), and he plays a minimum amount of tournies as it is, yet he still gets tired by the end of a tournament. He might need a bit of extra motivation from time to time, but hopefully he will find it when he needs it, just like he did at this past Wimbledon.
Also having a bit of luck in schedule and draws. He is one of the rare players that goes very deep in almost every tournament that he plays (semis and finals), and he plays a minimum amount of tournies as it is, yet he still gets tired by the end of a tournament. He might need a bit of extra motivation from time to time, but hopefully he will find it when he needs it, just like he did at this past Wimbledon.