How many years? About the same amount of years as all the rest of his new conservative ideas, about three or four, in other words just what everyone says, it was time to adopt a new persona for a new electorate base.
In 2005 58 year old Mitt Romney made the claim that he had an epiphany in a conversation with a scientist, a conversation that the scientist says didn't happen, that turned him from pro abortion to pro life, just in time for the beginning campaign for the 2008 primary.
However long that lasts...