If you ever come across any of my other posts, you'll quickly learn I tend to run counter to the other posters. So take what I say as an alternative view.

I don't let gallons/liters or hours dictate when to change parts on an engine. I go by measurements. As the rod and pins wear the head clearance and port timings will change. Once they fall out of tolerance for my desired application, then the engine goes under the scalpel. (if you didn't take measurements when the engine was new, you won't have any numbers to compare against)

As the engine accumulates hours, the rod bushings & pins wear in to one and other. As the surfaces become lapped during break-in the load becomes better distributed between the rod bushings and pins. As the fit improves the rate of wear slows down. Once a new rod is introduced to used pins, the new rod and old pins cut into each other and accelerate the wear on the parts.

So what I'm saying is don't change anything unless you have a good reason. IMO a few (3-4) gallons isn't a good reason. If your engine isn't running like it did when it was new, it's because of the wear. Reshim the head to account for the lost clearance, lengthen the pipe for the increased port timing. Changing a rod prematurely will only hasten the death of a mis-diagnosed engine problem.