She told me that I wore out my welcome and often stayed too long. It should be no surprise that your best friend would tell you about your faults. That is what best friends are for. If she hasn't been doing it, it is because she might be afraid you wouldn't be able to handle it. It may be that she feels a little intimidated by you and it is hard for her to confront you.
Most people have a hard time with confrontation.
It could be more than some people can handle. The idea is more for the kids to visit. It's hard for adults to visit and keep their eye on their kids to make sure that they don't get into other people's things. Talk some more with your friend and see if she feels a little overwhelmed by your visits. Maybe you could visit at McDonald's playground instead of at her home.