There is an initial purge with Retin-A where you will break out pretty badly for a while. Mine lasted a good 8 weeks or so. It was horrible and this is when many people stop using it. Don't stop! After this initial breakout, your skin will calm down and clear up. Hang in there!
My initial breakout lasted 3 months I'd say. I'm using ziana/biacna and I don't really think it was that successful on it's own. I finally caved and started taking minocycline just before my 6 month mark and I also added clindoxyl topical gel in the morning (I use ziana at night) because my acne was so persistent.
At this time though, my skin wasn't as irritated or dry as it used to be because it was used to the tretinoin, so I'd definitely caution using multiple topicals at first!