Originally Posted by ESpen36

Actually, it sadly does not work that way. When you apply to renew EITHER passport document, you are required to send in BOTH types of documents in your possession to verify your citizenship and identity. You cannot hang onto the non-expiring one to use in the meantime. So, for example, if you have an expiring passport book and a valid passport card, you must send in BOTH when you apply for just the passport book renewal. In the past, DOS has recommended that you put a yellow sticky note on the non-expiring document that says "DO NOT CANCEL-Proof of Citizenship Only." There is a risk that the passport office might mistakenly cancel both documents you submit, when only one of them is actually expiring, and the other was just to prove your citizenship (and should be returned to you without being canceled). So, there is really no benefit, and some extra stress, in having the two document types expiring at different times. Just my two cents.