My point is that time is not on his side. 23 is coming to middle age for a top 10 tennis player and his peers and his potential opponents over the next few years (excl. Fed) are the same age as him and are doing it (winning Slams) now.
It also pointed to tiger Tim to win a slam but he never did. Sampras and Agassi were too good for him. Will Nadal and Federer be that to Murray.
Except they're both probably gone in the next 3-4 years and Murray will still be in good nick. Murray's a far better player than Henman.