Platforms vary as to how effective posting can be. Firstly you need to think as to why you wish to communicate through social media. Are you looking for more contacts , friends or likes? Do you see your favourite platform as a community or as a way of monitoring your business.
Each platform has a particular dynamic which dictates both the style, length and demographic of the viewer. Viewers and listeners are very fickle and will look for posts similar to those they are already familiar with. I think within the business world the lengths and the regularity is simply down to content and the type of market you wish to promote to.
If you are promoting a service with a human interest you can post three times a week without boring your audience. However each post must follow on from the last one orby giving your post a fresh look. Video is probably the most popular these days and several short videos are more effective than less long ones.
If you are promoting a product you should post less regularly and only when there is something fresh to say. The public do not like to be advertised at within a personal post so you need to get their interest and trust before you can promote your wares. Posting does help the net give you a larger profile but it is probably necessary to spread your posting across many platforms. Each platform has its algorithms which control the post required.
Once you know the most popular style of post I recommend you adapt your message to that platform. The same message can be shaped to fit any system so it is appealing to your target audience and beyond .