dmrktrading

I should add that I usually use rolling 90 day T-bill yields (laddered 30-60-90d) as my estimate for RFR. It has the benefit of being defensible; gives higher ratios for marketing purposes, and cash sitting in the bank earning 90d yields really is kind of the default position for "I'm too scared to invest anything and I don't have any other ideas," which would be what you do when you don't want to take any risk.

However, if you are investing against a known set of liabilities, then you do have a known time horizon (basically the combined duration of those liabilities), and from there you can figure out what your RFR should be.