For a very long time, I would use it weekly, with great success. Applied it to my hair and scalp, and used for at least 30 minutes with heat. My results were always good soft, well moisturized hair, along with halted shedding.
I always recommend weekly deep conditioning, at a minimum. But I have deep conditioned 2-3 times a week and had positive results too. The key if you frequently DC is to ensure that you are using products for your hair that will not cause other issues with frequent use.
For example, my results if I DCd 2xs a week with a heavy silicone, or a strengthening (protein/polymeric) conditioner were not as good for my goals as when I just used a pure organic moisturizing DC. It's truly trial and error for the best routine that fits your hair care regimen, product choices, and your individual hair health goals.