The short answer is: at pre-Great Recession levels when the yield on the 10-year T note was at 5.0% or above.
Current forecasts for the terminal Fed funds rate are for 4.75-5.00 in February of 2023, which could push the 20 year+ paper exchange-traded fund back to near 2006-2007 levels between 80.50 and 82.05. (See, TNX, June '06 high, 5.245, correspondent with a TLT 82.56 low; June '07 high, 5.316, correspondent with a TLT 82.20 low).
If current bets as to the terminal rate are correct, we should fall short of the 2006 and 2007 levels, but could nevertheless be pretty darn close. And since current bets are that the Fed Funds rate doesn't come off 4.75-5.00 until much later in the year (the current forecast, is, ugh, November of 2023), this would conceivably require a good amount of time to work out.
As we've seen, however, things can change. A few months ago, bets weren't being made on a terminal rate quite this high and that a potential cut would come far sooner in 2023. But, here we are. Inflation could either remain "sticky," or come down rapidly in response to what the Fed has done so far, in which case, we never see the low 80s in 20 year+ maturity paper.
Naturally, if we do get there, I'll look to dip my toe in, whether it be with short puts (which would be a quasi-acquisitional play, most likely in my IRA) or something more directional, like a long call diagonal or a zebra/call ratio backspread ... .