Even on long term contracts, the yields will fall, and become far less attractive.
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Sure, those contracts are not open ended.
But some the oil/gas MLP’s are not producers. Plenty of pipelines delivery products are done this way. Some of the Natural Gas Liquid Suppliers did 7~10 year supply contracts before building the fractionators.
They are certainly not all in trouble, although many have had a significant drop in stock price at this time. Some good buys if you understand what you are buying and the associated risks.