They are like any other income investment: the higher the income, the greater the principal risk.
Most of them do best when energy prices are rising.
They send you a K-1, and in my experience, most of them send it late or at the last minute. If you own a few of them, it's a pain in the ass. Perhaps the best approach is to find an ETF or CEF that holds them so you do not have to mess with K-1's.