I will admit that I take all things on the DIS with a grain of salt and generally think people here (myself included) can initially overreact to a lot of situations at Disney. Thinking that people here were probably overreacting to this whole security check thing, I laughed it off and didn’t think twice about it. We are not a family who used the DND sign and never thought twice about having housekeeping enter our room. I do have kids who nap, but we were staying in a one bedroom villa on this trip so I wasn’t worried about a knock waking a kid in the bedroom.
But...we had an experience with the security checks on our June trip. It in no way ruined our trip, but it scared the crap out of my family and made me realize that maybe people weren’t overreacting to these checks.
We were at Old Key West. On our arrival night my mom and sister were asleep on the pullout sofa in the living room by 9 as they had been up since 3:30 that morning to catch their flight. My husband and I were having drinks at Disney springs, and our 4 year old and 1 year old were asleep in the bedroom. We didn’t have the bar across the door because my husband and I were out. At 10:00, my mom and sister were awaken by a man knocking on the door and then opening it! My mom and sister yelled because they were totally freaked out and the person said sorry he would come back in the morning. When my husband and I got back from Disney Springs around 10:30, my mom and sister were still awake, pretty shaken up by what had occurred. They’re not up on Disney policy/news, and had no idea about these room checks. I explained to them what I thought had happened, and the next morning I stopped by the front desk, let them know we had small children, and generally went to bed early anyway, so please do not come to our room after 9 PM!
The CM I talked to said they weren’t supposed to be coming by that late, and would make a note to please not come that late again. It didn’t happen again, but I was kind of annoyed that it happened in the first place.
So to answer your question...I have no idea on the rules about the timing, but they are definitely not following them in all cases.