It's up to you. Personally, I think not having them tests your skills as a writer even more, because you have to rely on your writing alone to carry your readers' interest from chapter to chapter. But then again, you could potentially get more input from more readers if you keep them intrigued by previews. I don't really favor either side, because I'll be seeing this one through to the end regardless. So it's really your call here, I think.