Yea, that could still happen but not as much any more with the rolling system. It also used to be 100 hours in a calendar month; now it's a rolling 672 hour (28 day) period. In December I blocked slightly more than 100 hours because on December 31 we only looked back to December 4, so what I flew on December 2 and 3 didn't count.

I'm a workaholic and I do often have trades/pickups blocked because it would make me illegal for some part of the months. My company's software looks at your entire month's schedule, so it'll block a trade/pick up if it would make you illegal for something already on your schedule later in the month.