I see the quality versus quantity of posts as a fair consideration. I see it all too often that people write just for the sake of writing, which isn't necessarily a bad thing, but one must ask if it is contributing substantive thought that may have had a chance to further develop with more time. I wouldn't limit yourself to a certain number of posts a day - simply write as you see fit, and if there are days where you feel you don't have much to contribute, find solace in knowing that there is no pressure to constantly deliver.