Back when I had plenty of hair, I always thought it grew more quickly in the summertime.
Now that you mention it, though, I did go two whole days without shaving this weekend, the first time I'd done that in about a year. Had quite a bit of stubble in the fringe area, but the top was still relatively smooth except for some minor fuzz. I don't know if that has anything to do with the time of year. I just assumed that I've reached the point where I'm about 99% bald on top.