Finding an acne product that works can vary from person to person. Two months is a good test, at least, to make sure it has lasting results.
If acne medicine should stop working for you in the future you may want to consider (website removed, this forum is not used for advertising products, feel free to PM amongst eachother) Otherwise, stay with what is working for you.
One factor to consider is whether the acne control medication is doctor approved and physician recommended. There is a lot of junk on the market and without a doctor approval it can sometimes be difficult (and expensive) to find something that is likely to work.