So you want to hole up in a CVS? What happens when another survivor group comes by and wants your stuff? Then proceeds to smoke you out to distract the zombies to get said stuff? May want to have a friend or two join you in your retreat bro.
Dude! He's in a CVS. Just throw sedative laced slim jims and bottles of wine out to the other group. After they fall asleep and the zombies get done with them go out and collect all their gear and weapons and ammo etc.