If they won't give frozen accounts back after that long, they should give you a reply before that time period is up.
I think you should have a year to get your account back, because that's how long it takes to get a reply from them!
I also think that after 2 years, accounts that haven't been logged into should be deleted. (I think their items should be donated to the money tree to put back in to play.)
Yeah, 2 years of inactivity seems a good time to delete the account. I like the idea of donating the items. too.