 You could post just once a year, and if that post deeply touches enough people that they contact you and want to hire you or buy your products and services, that could be enough. Or you could post five times a day, and none of it impacts people or not enough to sustain your business. So it's not about how often you post, but it's about how often you're willing to experiment, because you can't expect to post once, even once a month, and have enough experiments to know which direction you should go with your content. So I really recommend that you post as often as you're willing to experiment, and then do it lightly, and notice what direction your audience wants you to go to, and then post more things like that.