Don't obsess over what time you should post. If you post something good, it will be noticed. Posting poor content at the “perfect” time won't help you.
Facebook announced that they might be rolling out a "Dislike" button, which should help eliminate those awkward moments when several people "Like" a post about someone's mother dying. People mean well, but it can be the equivalent of giving a friend the thumbs-up sign during an open casket funeral.
I buy flowers for my wife whenever I sign a new client. I have yet to come up with a tradition for when I lose a client. But there are many possibilities. "That alternative band broke up. Here's some expired milk."
When you push posts from Instagram to, say, Twitter, the photo does not show up. People have to click the link to see it. And statistically, most people on Twitter never do.
Worse than not being on social media is being on social media, but doing it poorly.
So many people, companies, etc. create a Facebook page and then never do anything with it. You wouldn't open a brick and mortar store that looks like it is abandoned. You should not do that with your virtual storefront either.