Question about renew AP? Pjiang, pls help!

My question is: i will use my current AP to leave USA for a while, but this AP will be expired in December. Is it OK for me to renew the AP before I leave? If the renewal AP get approval before my current AP is expired, can I still use the current AP to come back to USA in November? Thank you very muc, pjiang. you are a big helper to most of us.