To me it depends on whether it is e-core. I won't use one personally (not hating, just preference). You can use the filter as long as you want to but I would suggest 5k is a good interval for the price. You plan on extending OCI I can't say enough good things about the Fram X-Tended Guard. I know it is pricey but it is so solid. I was amazed at the quality when I cut my first one open.
Go ahead and run it 5k, cut it open and see how it held up.