The playoffs run at the pace of when I get changes so I can't set a specific time, so be sure to get your extensions in sooner rather than later, preferably following the tips in this thread, especially if you're just starting negotiations with somebody.
I may work on extensions even after the WS if I haven't rolled over yet or I may not, so I wouldn't count on that.
Format arbitration cuts as follows
Team:
Position - Player x - Level (MLB, AAA, AA, or A)