The longest my DH has been sober during our 15 year marriage is one year. He routinely goes 6 months or so.
His anxiety is out of control the entire time he's not drinking every time he quits, even though he's on meds and sees his doctor regularly. He says that when he's sober he can't stay out of his own head. This is a horrible thing for me to say (and I would never say it to him) but there have been times during his sobriety when I've thought, "the drinking is so much easier to deal with than the anxiety."