Several months ahead. The constraint is obtaining historic corporate and payroll records from another jurisdiction, and the qualifying year must sit within the three years before filing.
The three-year window closes while the records are being found
This is the case where delay is genuinely dangerous. The qualifying year must fall within the three years immediately before the petition, so an employee who left the British affiliate two years ago has a window that is closing month by month, and time spent hunting for records consumes it. Begin by fixing the dates: when did the employee work abroad, for which entity, and when was that entity part of the group.
If the answer shows the window will close within a year, treat retrieval as urgent. Then allow for USCIS processing, which premium processing can shorten. Do not schedule the American operation around an unfiled petition, and do not assume that a long career with the organisation guarantees the year, because continuity abroad and the three-year window are separate tests and a case can satisfy one while failing the other.