The whole concept of Baptism of an infant is to show an action that the parents are Believers in Jesus Christ. Thus entrusting Jesus with the care of their child's soul if anything should happen to the child.
Some parents are not able to Baptize their child before the child dies of an illness at a very young age. Some of those parents are devastated their child was not Baptized before the child died. God knows all things, so those parents I comfort and tell them, they believed and God knows their hearts.
Baptized as an adult is an action that shows you are a True Believer in Jesus Christ. Some may never get Baptized, but still Love Jesus just the same. If you feel it is important to you to get Baptized again as an action to show your devotion to Jesus, then do it again for every action that we do that shows our devotion to Jesus is a good thing.
Some just go through the motions never knowing what it really stands for, what it justifies as an action that it was to show their devotion and belief to Jesus and that they accept Jesus as their Savior. Some of those will eventually realize it, some won't. But those that usually do get Baptized again just because it means something to them at that point and they realize what it means.
If someone asks me if they should be Baptized again, I always say sure if they really want to show their belief to Jesus, even if they were Baptized once before and didn't understand what it meant before, but now they do. One action can also lead to another, perhaps lead others to be Baptized as well. =)
God Bless.
