I agree, you must have a valid reason for missing the interview. Unless you do, I would go to the interview and simply ask the officer if they can delay the approval 1 week. They don't necessarily approve on the day of the interview, the officer may do you a favor.
This answer is for general informational purposes and does not take the place of a consultation with an experienced immigration attorney. This answer does not create an attorney-client relationship.
Not attending an I-485 interview in order to get the 10 year green card is not a valid reason. You should attend, preferably with an attorney, unless you have an emergency that requires you to postpone. Don't take risks with your future; follow the rules.
Answers provided by Ksenia Maiorova, Esq. on Avvo.com are of a general nature and do not constitute legal advice.
Disclaimer: This answer is for informational purposes and does not take the place of a consultation with an experienced immigration attorney. This answer does not create an attorney-client relationship.
As long as you are honest, it can't hurt to ask. Worst case--the Service says no, and you attend, and have to do the I-751 a couple years down the road. Best case--the agency says yes, and you can avoid the time and expense of the I-751.