I don't think there is perfect time for this. It could be early in life, it could be later than it was for all of your friends and family and it may be never, too. This depends on many, many factors and the age is certainly not the most important one.
A woman over 30 is only 8% likely to get divorced, according to marriage site http://www.theknot.com/— pretty good odds compared to 20% for those who marry at age 27-29! Cons: Contrary to popular wisdom, a woman's fertility only begins to dip when she's 28, according to the Center for Disease Control and Prevention.