Being born takes 9 months for us - and that's 10% of our lives before we are baptized.
As with most things, I try hard not to trivialize or reject how others feel the Spirit / experience God. Just as not all have all spiritual gifts given to them, I'm totally fine with not all having a sudden, spiritual rebirth - and I'm totally fine with accepting a more gradual "change of nature" (which really is the root meaning of "re-birth" in all our scriptures) as a real re-birth for many.
As a parser, there is nothing in the original Biblical statement that all must be "born again" that demands it happen in a spontaneous, instantaneous manner. There also is nothing in the pentacostal experience of the early disciples (recorded in the Book of Acts) that assures me that it was a true "re-birth" experience for anyone. Finally, in looking at the "re-birth" experience in the Book of Mormon when King Benjamin spoke to his people and they felt no more desire to sin, it is apparent from the following narrative that the experience didn't "take" with some of the people. It wasn't long before many of them were sliding back to their previous ways. I think we are influenced heavily by the interpretations of others concerning the term "born again" - and I don't believe that those interpretations have to be Truth.
Frankly, I know WAY too many people (most outside the LDS Church and a few inside it) who have felt an over-whelming experience they have termed a re-birth who subsequently have slipped back into their old lives to believe that "becoming a new creature in Christ" has to happen immediately - that a more gradual "becoming" can't constitute being born again in a real and powerful way. In saying that, I'm not trying to diminish or dismiss the sudden and obvious re-births that do occur and last; I'm just saying I think the ultimate result of being born again isn't encapsulated in those types of experiences for me and many others.
Perhaps I would summarize my view in the following manner:
"To some is given to be born again in an intense, 'immediate' experience, while to others is given to be born again through a steady, 'gestational' experience."