Not Finishing Yet Recommending Series

Have you ever recommended a series without reading all the books in it? The story goes, one of my friends asked me for a recommendation for an older woman who had read Divergent but was not pleased with Allegiant. It sounded like she wanted something similar, but with a different sort of ending, and based off the blogger reviews and discussions that came of two falls ago, it seemed like the Legend trilogy by Marie Lu was more up her alley. I was right; she really enjoyed the series. But before knowing that I was right, I was really anxious. I hadn't actually read Champion myself and yet I'd recommended the series...?

That time it had worked out, but I can't help but wonder, with regards to my reviews page (which is essentially a giant recommendations list), whether I might not be so lucky more than once.

For that matter, another friend, after I told her that I wasn't planning on continuing a different series, was like, wait what? Why? As she'd said, she wanted to know what elements made me not want to continue in a series. But as I told her, it wasn't anything particular. If a first book was good but I'm not invested enough to want to continue, then I won't. I'd have no problem recommending that first book though. (Now Champion, I'm still invested in that trilogy and I do plan on reading that book.) And lately I wonder if that sort of policy is unusual.

How often do you finish series? For me it feels like there are TONS and TONS of unfinished series on my shelves, and I have no desire to go back and finish most of them. It's the rare book that makes me think POTENTIAL or OMG I LOVE THIS or CURIOUS TO KNOW WHAT WILL HAPPEN, and those books often make the lists that I create for myself (15 TBR books this year; 10 books I'm looking forward to reading in 2015, etc.). Which then makes me wonder - well, if I have no desire to go back and finish those books, is it really a good thing to be recommending the first book or even the series at large?

So in the end, what do you do with unfinished series? Do you feel comfortable recommending them even if you don't know how they'll end? Can an ending change how you view the first book (which you'd loved)?