One area of difference between Credo and Paedo assumptions:
I once heard a baptist pastor make the point as follows: "I once asked a person how long have they believed in Jesus, and he replied, "Well, I have always believed!"... and I had to look that man straight in the eye and tell him, "Well, that is a little too long!" Their must come a POINT OF DECISION in your life, and you must choose Jesus!.
The Baptist minister's point is that you must personally come to a point of repentance and deciding for Christ. The emphasis is often on dramatic conversion and decision. We see this emphasis in the Book of Acts.
A Presbyterian minister, however, sees children as being in the covenant and slowly being nurtured into the faith. They will quote the psalms about praising God from their mother's breast (and those references are, indeed, in there), and YES, I have met people who have seemed to always be Christian from toddlers even.
And so there is often a different emphasis: Decision versus Nurture.
In my tribal ministry we've seen both, and the believers we trust who are the most spiritually mature now are those who were nurtured first and then made a decision (often being forced to) and then continued being discipled.
Conversion happens in a moment in time, yes, but it seems like a process to the human eye. That is why we've now focused on evangelism-through-education and schooling the kids and discipling them with the bible during the school day.
The older tribal men who lived a life of warfare and evil have made decisions for Christ but many have quickly returned to threatenings when mad, etc., such that we have no trustworthy believers over 35 (we have some we believe to be saved, especially old widow women), but it almost seems the older men are too stiff or learned in their evils that they cannot depart readily. They've worn ruts of evil into their lives and the continually retread those paths.