whistleway
Semi-Pro
Here's an analysis of multiple grandslam winners when they won their first grandslam in Open-era. So, all champions who won their first slam before 1969 are not included.
As you can see, there is no set age at which a player has to win his first slam and then go on and win at least one more. The age band seems to be around 18 to 25. This should bode well for the young players like Gasquet, Djokovic, Murray, Berdych, Baghdatis, and Ancic.
There are 23 multiple grandslam champions who have won all their slams in the open era. Here's the data:
If there are any errors, please let me know. Thanks wikipedia for great info.
http://en.wikipedia.org/wiki/Chronological_list_of_men's_major_tennis_champions

As you can see, there is no set age at which a player has to win his first slam and then go on and win at least one more. The age band seems to be around 18 to 25. This should bode well for the young players like Gasquet, Djokovic, Murray, Berdych, Baghdatis, and Ancic.
There are 23 multiple grandslam champions who have won all their slams in the open era. Here's the data:
Code:
[SIZE="2"]Name Year Grandslam Slams Birth Date 1st Slam (Yrs, Mn)
Jan Kodeš 1970 French Open 3 1-Mar-46 24 03
Stan Smith 1971 U.S. Open 2 14-Dec-46 24 08
Ilie Năstase 1972 U.S. Open 2 19-Jul-46 26 01
Jimmy Connors 1974 Australian Open 8 2-Sep-52 21 04
Björn Borg 1974 French Open 11 6-Jun-56 17 11
Guillermo Vilas 1977 French Open 4 17-Aug-52 24 09
John McEnroe 1979 U.S. Open 7 16-Feb-59 20 06
Johan Kriek 1981 Australian Open 2 5-Apr-58 23 08
Mats Wilander 1982 French Open 7 22-Aug-64 17 09
Ivan Lendl 1984 French Open 8 7-Mar-60 24 02
Stefan Edberg 1985 Australian Open 6 19-Jan-66 19 11
Boris Becker 1985 Wimbledon 6 22-Nov-67 17 07
Pete Sampras 1990 U.S. Open 14 12-Aug-71 18 12
Jim Courier 1991 French Open 4 17-Aug-70 20 09
Andre Agassi 1992 Wimbledon 8 29-Apr-70 22 02
Sergi Bruguera 1993 French Open 2 16-Jan-71 22 04
Yevg Kafelnikov 1996 French Open 2 18-Feb-74 22 03
Gustavo Kuerten 1997 French Open 3 10-Sep-76 20 08
Patrick Rafter 1997 U.S. Open 2 28-Dec-72 24 08
Marat Safin 2000 U.S. Open 2 27-Jan-80 20 07
Lleyton Hewitt 2001 U.S. Open 2 24-Feb-81 20 06
Roger Federer 2003 Wimbledon 10 8-Aug-81 21 10
Rafael Nadal 2005 French Open 2 3-Jun-86 18 11[/SIZE]
If there are any errors, please let me know. Thanks wikipedia for great info.
http://en.wikipedia.org/wiki/Chronological_list_of_men's_major_tennis_champions