Fabian has a point, retin a or any retinoid will take months to work. I was on a low dose accutane course (only 10mg per day) and it took me about 8-9 months before I could say my face is clear. So on a topical retinoid I would say it is very much possible to break up to 6 months and it does not mean its not working. it does but very, very slowly. But the end results are worth the wait, plus when you've been on it for a year your skin will have adapted to the retinoid so you wont get the excessive peeling and redness anymore.
You may read this and think what I've got to wait nearly a year for this to work??! but i will say the end results are very much worth it, so don't give up