5 months? that seems like a damned long average. Very first grow i did i did 4 weeks veg and 8-9 weeks flowering, under 1 week drying (just under 3.5 months total) and each plant yielded 2 ounces.
Unless you are using poor lighting, then 5 months should EASILY see you 3-4 ounces.
More details though. We can only give you our best advice if we know what conditions you are working with. do you have an HPS, what size, are you using a tent, or a small cupbouard, etc etc etc. All of these are important factors.