Britney Spears is on her way to overnights with Sean Preston, 2, and 1-year-old Jayden James, OK reports.

"Britney's progress over the last two months is good," admits Mark Vincent Kaplan, attorney for Brit's ex-hubby Kevin Federline, to OK!. "But it's premature to say that two months shows a pattern of consistency."

"We need to see a steady, consistent trend of behavior for a while," explains Kaplan. "The goal is consistency over time with nothing at all out of the ordinary."

Kaplan tells OK! that he anticipates the custody battle will go all the way to a trial.

"Kevin's goal involves primary custody but also involves his desire to see Britney become, over time, a solid and substantial figure in her boys' lives," he tells OK!. "And she is inching toward that."