My boys are past planned sleepovers but had them at our house, and went to friends when they were younger. Up until about age 10, we knew the parents well. In middle school, I just had to trust my instinct. Now, it's more of a "hey, it's late, can I stay here, Ms. Cathie?", or elder dh will call and say "it's late, I'm staying at so and so's house". So far, it's mostly been just guys. Except for once, and the young lady slept in ds's room, he and the other guys got floors and couches. She was not the gf of any of the guys, not that it would have mattered, her parents didn't want her driving home in the storm.