I’m not quite sure what you’re asking, so I’ll just say what comes to mind.
When a person stays around, it is their choice. We can’t keep someone around by willing it alone. They have to decide to stick around. And the Force doesn’t care how long it takes for you to transition fully to the other side. Time does not exist outside of our 3d universe, so when a person stays around to watch things for a century or two, it is just a moment on the other side.
Now, I do know that sometimes these people can be pushed to transition because they’re needed for something else. Perhaps they tend to go through life with someone else as a partner, and that person would like them to come back to go through another incarnation. Or perhaps they have something that they need to be working on while on the other side. We can all still choose to do things while non-physical, according to Sylvia Browne and others. So, sometimes we need to have a little reminder that we should let go of the physical world so we can come back in human form.
Does that answer your question? If not, please clarify and I’ll see what comes to mind.