Church records can be used for more than verifying the details for births, marriages and deaths. They can alert you to the religious customs of the times. The age at which a ceremony was performed may vary, the type of ceremony and whether it was done as an individual or a class could change. For instance in the Archdiocese of Chicago during the early 1900s the Sacrament of Confirmation was received as part of a class with one sponsor for all of the girls and one sponsor for all of the boys. Records kept would depend on the specific religion.
While searching for an individual in the Norwegian records and trying to determine which of several Martin Hansens born at about the same time was the correct Martin Hansen someone (I wish I remembered who so I could give them credit!) suggested that I check the confirmation records to see which of the candidates had survived childhood. Confirmation was required of all Norwegians between the ages of 14 and 18. Checking the Confirmation records did reveal the correct Martin Hansen along with his parents. Working back from there I was able to find the Christening record and also the records of his siblings. This method could be used with other religions that have other requirements for older children (communions usually at age 7 or 8, and confirmations usually at 13 to 15)
Swedish church records include a "Husförhör" which is a household examination listing everyone, including children, in a residence. Included in this listing are names, birth dates, relationships and details about when people left a residence and where they went. This can be extremely useful in tracking immigration.
On occasion, those same helpful church records can prompt more questions than the solve. My dad's parents (he a Luthuran and she a Catholic) were married in a Nuptial Mass at a Catholic church in Milwaukee at a time when "mixed" marriages were not allowed to have a Mass. A year later they were godparents to her nephew at a time when both godparents were required to be Catholic. He was buried in a Catholic cemetery when again the Catholic Church rules did not allow such a burial. I've given up trying to find an explaination and just accept the facts. No he never did convert.