At what interest rate would a refinance no longer make sense?

[Andrey Y.]

I have investment properties with fixed rates of 3.375%, 4.5%, and 4.375%. There has been several six figures $$ in equity growth over the last several years, and my LTVs have recently been pushing 50%. I am looking to refi one or more of these back up to at or near 80% LTV, to pull out all that equity just sitting there.

I know interest rates are up, but at what point (0.5%, 0.75%) etc. higher rate would you say that it wouldn't be worth doing this? I appreciate your feedback.