I just renewed my AZDHS MM card even though my original card doesn't expire until the end of September. My understand (from reading on the AZDHS website) is: If there is a Dispensary OPERATING within 25 miles when you RENEW your card, your lose your rights to cultivate. They won't be looking up patients that have existing cards and asking for a "redo."
Also, I was surprised to see that even though I renewed the first week in August, the RENEWAL Card doesn't become effective until my original card expires at the end of September. My renewal card keeps the original expiration date. So even if someone opened a Dispensary next door tomorrow, I can still cultivate. Again, the right to cultivate is determined when you RENEW, not after you get your card.