When you come across some era of history you've never heard before that might be fascinating, or an obscure but highly recommended book on conflict management, or you come across some primary source papers that are largely unread any more about an important event - jump on it right away.
You'll never really be motivated to read Baldissare Castiglione by Julia Cartwright. It's an obscure-ish book, cited not particularly often, about the 17th most interesting guy in the Renaissance. He hung out with da Vinci, and Borgia, and met all the Popes of his lifetime, but you'd have to either really love the Renaissance, or come across Il Cortegiano in research to read him.
Baldis-who? If you don't look him up now, it likely won't come up later.
A lot of good strategy and being a successful generalist is about picking up obscure skills. Steve Jobs talked in his famous Stanford address about how the class he took on calligraphy in his late teens became one of the drivers behind the Mac being the first computer with beautiful typeface.
There's plenty of calligraphers in the world, but how many calligrapher-entrepreneur-designers? A good mix and synergy of skills gives you the ability to make a contribution. A good mix and synergy that includes something obscure can help you make an original contribution.
Problem is, you won't know what that is in advance. So I say chase down the fleeting impulses. I don't know, he didn't say, but I'll hazard a guess Jobs got bored with calligraphy soon after, and didn't make it a major focus of his life. If he hadn't studied it when he did, he might never have done so.
With that said, I'll end with the note that you shouldn't get too into the obscure and fleeting. Don't forget to pick the low hanging fruit, those books and lessons and disciplines that are so massively amazingly insightful that you get immense amounts of impact from them. I think it's easy to get fatigued of a work you've never read but heard about too much, and thus miss out on something important. That's what happened to me with Think and Grow Rich - I only barely started reading it, and I'm kicking myself for not reading it earlier. Don't get too into the obscure and fleeting that you forget to pick those really large, juicy fruits of lessons.