FWIW I've had the same pin in my almost never-removed 2005 F150 2" receiver/drawbar since new. I did pull it awhile back to briefly borrow the drawbar for another vehicle, the pin looked like new still. That's a Reese branded pin and drawbar so likely of good quality to start with. The 'loaded in shear' strength of those pins is huge, they don't 'flex' in shear so I don't think "metal fatigue" per-se is a likely failure mode.
That hitch has pulled many, many, loads from ~7k# trailers loaded with tractor, etc. Methinks barring some extremely corrosive environment it's not an issue, but as Dave says, I'd replace it at the drop of a hat if I had any concern or worry at all.
Just one opinion, Have Fun!