As a social media manager and marketing specialist, I advise clients and friends to post no less than 3 times a week. On platforms like Twitter, you want to post more often. 

The reason is clear - the more you post the more people see your content. Right now, for organic reach, only about 7% of your followers on a site like Facebook will see your posts. You can share to groups and on your timeline, but still, it's not the same as being an active contributor to your community. Engagement builds a stronger profile and offers insight to your prospective clients as they move through the buyer's journey.