Hi SdSearch. Thanks for the information. I didn't know "Chase business cards don't show on credit reports". That's interesting if it is truly the case. My business is a sole prop using my SSN however, so I don't know if that applies in my case.
Indeed, I don't want to decrease my average length of credit history by closing a card, which would affect my credit score. That's my main concern.

Also, you say that one "can't downgrade a business card to a personal card". So Chase meant the "United MileagePlus Club Business Card" as a conversion and not the "United MileagePlus® Club Card" ?
I am a bit confused here as well.