It's Shorter in Dog Years
There’s got to be a statute of limitations for how long you can haunt a place right? I mean you don’t see that many Caveman Ghosts out there do you?
If you really want to haunt a place for a long time you have to be buried, or have died, with a bunch of likeminded people. If enough of you died in the same place you can get a couple extra centuries! Indian burial grounds and old cemeteries from the 1600’s? Totally haunted! But a single dead Indian? 50 Years tops!
Also, it helps if the place you died already looks creepy. That way people will attribute the random gusts of wind, and occasional noises you produce as something a ghost did instead of just the wind. It must suck for the people who were horribly murdered in a nice sunny park.