Glad you are having initial success with Duac. I, too, was using it for quite some time last year and it worked great! I hardly ever had bad breakouts. And if I did get a few pimples, it would dry them up fast!
Unfortunately, I don't know if the Duac wore off, or the BCP I was on (OTC-Lo) got to be too much for my hormones, but my skin basically exploded in acne after about 6 months on Duac.
When I did use Duac, it was one of my favorite topicals. The only bad thing I noticed was that my pillowcases were somewhat discolored from the BP...so perhaps you should use light colored pillowcases.
I hope that it continues to work for you in the long run! Best of luck!