mixed results.....I think you will get mixed results; so here's the first half of the 2 kinds of answers you're probably going to get:
I like my apple dry dry dry. I mean when I split it, I want it to sound like a broken baseball bat clanking together. So, I say at least 6 months. The stuff I'm using this year, I cut down early last summer.
If you have a bunch, and don't mind wasting a small percentage, you could start a fire outside your smoker and cook the green apple down to embers. Then scoop the embers into your smoker. Much less chance of creosote buildup.
I will mention that I'm a wierdo when it comes to apple. I like to cut thin slivers of the stuff and set it on a hot plate in the house, just for the sweet smell (yea, I get in trouble from the boss!)