From what little I know I think you have to pay a fee every year to keep your patent current, the figure $200 comes to mind.
The old lady that invented the Fugit Spinner let her patent lapse because there was no interest at the time and she felt no need to continue paying the fee, someone else took it over and made a gazillion dollars off the idea.
I never felt the need to patent my tillering gizmo idea although it could be done, I just didn't want the hassle.