It's only recommended that Arimistane be taken for an 8 week period. However, I know many have used Alphamax for a longer run than 8 weeks. I wouldn't recommend it, but if you're not having any side effects (dry joints or aches) and you're seeing good results then you might enjoy experimenting with a 12 week run.
I'm not sure if you've gotten your second bottle of Alphamax, but Performax just released the new Alphamax XT which doesn't contain Arimistane. Alphamax XT would be perfect to run the 4 weeks following