Due to a combination of factors, the xB didn't get an oil change for almost 7,000 miles, on a 5,000 recommended interval. I bought 2 filters & plan to do a shorter interval change to help flush out any gunk in there.

What is a good interval to help clean out any ick from having gone too long(engine has 217K so it also could generally use the cleanout)?

1,000 miles? Few-hundred miles? X number of hours driving plus immediate oil change?