I have brooded on the matter of baptism ever since I was a Christian. These are my conclusions - which have been stable for about five years, so far.
Baptism is not necessary to salvation. When considering that God is the creator, and loves us all as his children; it is to me inconceivable that he would have made it necessary to undergo baptism as a condition of salvation.
When it happens, it seems to me that baptism ought to be done as it is described in the New Testament - by total immersion, and as soon as a person has decided to become a Christian.
That is, baptism should ideally (but not necessarily) be the first thing in a person's Christian life; baptism without delay; baptism as soon as a person wants to pledge that Jesus is the Son of God and his Saviour.
Other forms of baptism I regard as having been co-opted into the specific, and contingent, needs of a specific church or denomination (as can be seen from the changing history of baptism, both between- and within-denominations).
Such extended and elaborated forms of baptism may (in a particular time and place and situation) be a good thing, may indeed be a very good thing - may strongly promote theosis (i.e. the spiritual development of the individual towards divinity as a Son of God); but, in my understanding, there is no direct link with either salvation or theosis.
Note: Most importantly to me, I have sought confirmation of the above by meditation, prayer and revelation. I am confident that this is valid for me - but that fact does not imply universal validity for all persons in all times and circumstances: some specific people may need to be baptised. My own baptismal status is having been Christened as an infant in the Church of England, by application of water to the forehead... this strikes me as, overall, one of the least valid of all forms of baptism.