I ran a large fleet (over 200) of Caterpillar 3516 generators in a former job. We ran them very hard, with normal load over 1000 kW.
In most cases, we did top end overhauls @ about 25,000 and bottom end at 50,000 hours. Oil changes were done at 900-1000 hours.
One of the biggest variable affecting the engine life was the number of startups. The engines that ran during peak hours only, and shut down during the night had a much shorter lifespan than those running almost constantly.
1meg is not a lot for a 3516. In a standby application they go up to 2.5 meg. In a prime application they typically are slow speed 1200rpm and much lower kw rating than standby applications.