I stuck with one for a long while. Sunflower for months and months. But when I broke free, I went crazy. I pull one thing in the morning, and another in the evening. I can't see any harm in doing it either way. But in hindsight, I would actually change every month or so.
My teeth look amazing when I do hemp in the morning and coconut in the evening. And very recently, I think it knocked out the flu. I've been literally surrounded by pestilence at home and at work. I have been waking up with clogged sinuses, headache and itchy throat. My first pull of the day takes it all away. If it comes back, the evening pull does it again.
I haven't been sick in one year.