My Developer Program Membership (along with the iOS Distribution Certificate - it seems) expires in a couple of weeks. About a week ago, Apple sent me an email implying that I must renew the certificate before it expires in one month. However, I expect to submit some apps in at least a couple of months, and I would prefer to wait until this time to renew my certificate. Can I do this long after it has expired, or must I renew it before the expiration date?
You may renew your Developer account whenever you want. Just keep in mind: All your 'live' apps in the App Store will go offline when your membership expires. When you renew the Developer Account you can bring the apps back to the store again without setting up / needing a review proces.
I had the same with a customer of mine, their membership expired for several months (they just didn't care enough) and they renewed the account without any hassle.