I cancelled my subscription around March 2012 and am itching all over to come back soon. I used to have a hunter with tons of achieves, companions, exotic pets, etc. I'm coming back regardless if he'll still be there along with my mage, but I don't want to be caught blindsided when I log on and see my list of toons completely empty.
Inactive characters don't get deleted. I have two accounts, one of which I haven't used since 2009 before battlenet accounts were a thing. I recently activated it and all of my characters were still there. The only thing that may happen is if someone name changed, blizzard may open up the name of your character for someone else to use. Other than that, the character itself will still be there.
Awesome! Man, you just made my night. As a fellow player I don't think I have to explain how much effort and determination was fed into a main toon. That hunter gave a damn good name to both hunters and dps. It's about damn time he wakes up and once again proves what a well-crafted hunter can do.
I hope to be back within a month. Can't wait.
To add on what Drax3 said
Around two to three years ago, I deleted everything on my account. Recently got back into MoP (Loving it) and I talked with a GM, they were able to virtually get back 90% of what I deleted. I was astonished and while I in no way would not trust a 100% chance at recovering; even if you delete your characters, they still keep the data “there”.
Lucky you I guess. I quit playing for a couple of years just before ICC opened up. When I decided to resub three months ago, my gear was sold/disenchanted. The GM told me they were unable to recover the items because the log only goes as far as three months back.
As for OP's question: your characters should all still be there, provided your account wasn't compromised in the meanwhile.
That's incredible. Kind of makes sense, though: A few years ago I hadn't logged on for about two weeks (I was in training). I got an email stating I had changed my password so I did what I could to get a hold of a laptop and logged on. My main and alt were stripped of their gear and whoever had hacked it was trying to transfer my toons to another server. A couple of days later after talking with GMs, I had all my stolen gear, items, etc in the mailbox. It was magical. For that moment, I believed in Santa Clause.
BTW, how is MoP? I played a bit through Cata and have no idea what to expect. I read through the “What's Different?” post under the FAQ, but I'd like to hear from a player.
Forever. It's just space to them which is relatively cheap. The only thing that might get changed is your toons name because after a certain amount of inactivity someone active can “request” a name change and if they want your name they will release it.
Not only does Blizzard not delete inactive characters, it is usually possible for them to restore any characters you have deleted yourself. Just submit a ticket.