Okie's example is great, I personally use two cascading counters triggered off of a RTO.DN bit. Counter 1 counts 0-32767, and when it reaches 32767 it increments the second counter and resets itself. The total is then calculated as:
Counter1.ACC + (32767 * Counter2.ACC)
This gives a max of 1,073,709,056 counts, which if your pump lasts that many hours, you've definitely gotten your money's worth. If you really needed more than that you could implement a third counter. I've used this logic frequently for number of starts, flow totalizing, and running hours. Number of start and flow totalizing bypass the RTO, just the start/flow total pulse bit into a one-shot, straight into the counters.
Again, Okie's example is probably a bit more elegant, but I frankly haven't experimented with long integer (LINT) data yet. This was my workaround for the limitation of 0-32767.