My daughter’s grips were broken in (as in fit her hands and nice and flexible) in a few weeks, but she didn’t become accustomed to them for months. I think it was probably a good nine months before she stopped saying they made everything harder. Her gym doesn’t introduce them until level five so she had years to get accustomed to working without them.
My kid got her very first pair and was doing bars normally in two-three practices. I did get her narrow grips with a reputation for breaking in extremely easily.