As often as you can share content that is interesting for your target customer, and worthwhile for your business.
To be honest this question is a bit nauseating to me. Particualrly when ‘experts’ prophesies a definitve answer.
You know what; people and business have gone viral and gained thousands, if not millions from single pieces of content.
On the other end; there are businesses that share on multiple platforms every day to the sound of crickets.
Produce something useful; share it.
Genuinely entertain your audience, and share it.
Do something newsworthy, and share it.
On social your competition is not other businesses. Its mostly family and friends.
That is pretty stiff competition, so you better be on your game.