Ah, Delta usually starts making changes to their flights as soon as I book with them. Just kidding. Well sort of anyway. Whe we book way in the future, the airlines can be counted on to make many changes. I booked a Dec flight with Delta about 4 months ago. It has changed three times now. Every time I have to call them and get my seats reassigned. A real pain.
So, it makes sense to check on your flights every few weeks or so. Then, when you get closer, the 3 mo mark, I like to check weekly. Then, when I get to a month before traveling, I check every day, right up to travel day.
I started flying with JB because they never changed their schedules. That's why we have to wait so long to book with them. They figure out their schedules and then we can book 'em. But, I'm finding that even JB is changing their times now...even cancelling flights at the last minute. Ugggh.