I've heard about the Canon 1DX throwing oil onto the sensor from the shutter mechanism. I never owned one so didn't quite appreciate the issue, but my 1DX Mk II makes quite a mess if you look at the sensor at the level of detail I do.

I'm wondering if this is something that tapers off with use?

I suppose it's not a bad price to pay for 14 fps and a long shutter life -- something has to lubricate the moving parts. The oil spots are tiny and wouldn't show unless you really know how to see the state of the sensor, but after a few days of shooting something like 500-800 images a day, many in bursts, I wouldn't like to think about letting them accumulate for long.

I show a good way to see the state of the sensor and to clean the oil in a tutorial on my web site.