Its a mindset on whether or not you truly want to achieve sobriety. If breaking it down to 30 days helps, I say go for it. But if you plan to celebrate at 30 days and drinking your brains out, then its pointless.
I made staying sober the most important thing in my life for a few months and then the grip kind of let go. At 49 years old I set a goal of remaining sober until I'm 60 and then I'll reevaluate. Sounds silly, but that's my goal.