I constantly make notes about clients. I compile facts, quotes, information about their background, gear, songs, etc.
When you have potentially 365 days of posts to do, it is best to have more content than you need and to have some of it compiled ahead of time. Sure social media is great for spontaneous moments, but that's not something you can rely upon.
And I think that is where a lot of bands and businesses run into trouble. They wait for inspiration and expect it to hit every day. Sometimes the muse will visit you, but most of the time you are going to have to forge on without her.
Running a decent social media profile involves being a kind of modern day journalist. You have to find the stories. You have to track down the interesting bits of info. You research, interview, compile, organize, write, and edit. And you kind of have to do it every day if you want momentum and stamina.