You may be legal but are you right for me???

Many believe or say that age is just a number.  Sometimes we try not to discriminate against someone just because they are younger than us.  We say that we can't date someone because he or she is too young. They may not be mature enough is the though that floats through our head.  But how can we be sure that the 21 year old we met last week we be any less mature than the 31 year old we met last night?  Is age really just a number or is there some truth to the thought that maturity comes with age?  Personally I have only had one relationship were I dated a younger man and let me just say that will NEVER happen again.  I know that I shouldn't let one experience spoil the rest of the experiences that I may have.  But if you met the guy I was dating you would understand.  Maybe it was his age or maybe it was just the person he was but lying was part of his m.o.  I wonder though do men have the same feeling when it comes to dating a younger woman?  I have never had a problem with older men telling me that I was immature or that they could really tell there was a gap in our age.  So if you are over 18 does that mean that you are mature enough to date anyone older than you or is a person by person situation?  When it comes down to it does age really matter?  If I were 40 and dating a 30 year old would there really be that much of a difference in our states of maturity or do I just see the age difference because my ex is just beginning to be an adult?  Yes 21 is old enough to vote, drive, drink and pretty much do anything.  But I'm not sure that 21 is old enough to date 25 and above.  I may be biased and sound kind of stuck up but in my humble opinion a 21 year old "man" is no where near mature enough to be involved in a serious relationship with an older woman.  What are your thoughts?