Let's back this up with some facts since I'm not doing much this afternoon. Multiple male grand slam winners since 1980.
Name, total number of grand slam titles, age at first grand slam win
Bjorn Borg, 11 GS, age 18
John McEnroe, 7 GS, age 20
Johan Kriek, 2 GS, age 23 [won 2 Australian Opens when most of the top players didn't bother playing]
Mats Wilander, 7 GS, age 18
Jimmy Connors, 8 GS, age 22
Ivan Lendl, 8 GS, age 24
Stefan Edberg, 6 GS, age 19
Boris Becker, 6 GS, age 18
Pete Sampras, 14 GS, age 19
Jim Courier, 4 GS, age 20
Andre Agassi, 8 GS, age 22
Sergei Bruguera, 2 GS, age 22
Yevgeny Kafelnikov, 2 GS, age 22
Gustavo Kuerten, 3 GS, age 20
Patrick Rafter, 2 GS, age 24
Marat Safin, 2 GS, age 20
Lleyton Hewitt, 2 GS, age 20
Roger Federer 16 GS, age 21
Rafael Nadal, 8 GS, age 18/19 [birthday around the date of French Open final, can't be bothered checking]
So there you have it. Of the 19 multiple grand slam winners from the past 30 years, only 3 of them won their first one past the age of 22. Kriek doesn't really count as the Australian Open in 1981 and 1982 featured hardly any of the top players and was just another tournament in the eyes of most people at that time. Lendl and Rafter were 24 when winning their first grand slam - Murray is 24 in May. Lendl is the only player to have had massive success who didn't win a grand slam by the age of 22 (Rafter and Kriek "only" won 2). Time is ticking for Murray.
If you're going to argue this one garymcc1874, please make sure your facts are correct, thanks.