Hi -- one thing I should mention (what makes us special) is that we offer all our RIs with guaranteed buy-back. So you're getting the 57% discount of a 3-year no-upfront RI, but have the option to sell it back to us anytime after 30 days. Guaranteed.
So you should actually buy the RI for the instance you plan on shutting off, and then we will buy it back when you shut the instance off.
Feel free to ping me directly if you'd like: kaveh@usage.ai