We also got in during the high rates, but I've decided to have them as a permanent part of our portfolio as an inflation hedge. They're also a deflation hedge, since the rate can't go below 0%.
Between our two accounts, I sold just about all 100k we had in January and re-bought at the fixed 1.3% interest rate, using the gift box option. Note that doing this means I'm committed to taking 5 years or so to have access to this money again. Our EF is elsewhere, and we plan for this to be a long-term position. If the fixed rate goes up, I'll probably buy some more via gift boxes and transfer to our accounts over time.
We're planning to pursue a glide path at some point, and I'm anticipating that I bonds will be 5-10% of our portfolio when we retire. I might also do a TIPS ladder (not TIPS fund) at some point. We have no pensions and no other guaranteed income at retirement except for social security. I plan on having 40% in bonds / cash right before retirement, and I bonds will be a part of that.
The exemption from state and local taxes also makes I bonds more attractive for us.
My parents, on the other hand, have generous pensions in addition to social security that more than covers their living expenses. Their guaranteed retirement income would also cover the majority of long-term care expenses, should one or both of them need it. They also live in a state with no state / local taxes. I advised them to sell their I bonds and not re-buy. They are pretty much invested in 100% equities.