I recently got a Lenovo B575 laptop off of Craigslist and so far I'm pretty happy with it. Before I got it, the girl informed me that the battery only lasts 3-4 hours and I told her that's no problem. I just ordered a replacement battery for it today, anyways.
But one problem I have noticed, that's really starting to get on my nerves, is the fact that the laptop will randomly go into sleep mode by itself. There doesn't seem to be anything to trigger it, it just does it out of nowhere. I've already checked the power settings and I disabled the sleep mode settings, so it's not that. And it'll go into sleep mode whether it's plugged in or not, even when the battery is fully charged.
I'm not sure what's causing it or how to fix it, but other than that problem it's a pretty great laptop, I have no other complaints. It's just extremely annoying having it go into sleep mode by itself randomly, then having to wake it up and sign back in.