This is poorly thought out.
If the 3yr rate gives you a saving or you think rates will move up then it is not a poor strategy to fix for that long, hell I would fix for 10 years at 6% if I could, who cares if the rates go to 5%, so I would be paying a little bit more than I could have been, but I have certainty.
I agree. I fix rates for SANF of certainty knowing my portfolio's insulated from economic fluctuation. Any cash flow advantage from a rate rise post fixing becomes a bonus. If rates drop post fixing that becomes my premium paid for SANF.