As a 38 year old I think I should be able to sleepover with friends whenever I want. However, a friend may consider it a little odd for me to want to stay the night unless I am too drunk to drive. As for my children, I have no issues with them having sleepovers here. I will not allow them to sleep at other friends houses though unless I know the parents extremely well.
You should be able to have sleep overs with friends. When you have friends sleep over, you gain a valuable bonding time with all of them. It is a great way to become closer to your friends and under stand who they truly are, outside of school and other people.
I host them often for kids in our high school and 20 something youth groups.
They give youth a chance to be together as a group up late (no sleep) and get to know each other better than a 2 hour tightly scheduled event.
In the laughter of sleep deprived xbox and trampoline we talk on many serious subjects as well.