It also works to a limited extent if you think the high interest rates on I Bonds are only temporary. You can buy a gift for your spouse and hold it in your gift box. Have your spouse do the same for you. Wait until interest rates drop and the two of you don’t buy I Bonds anymore. Then you can deliver the gift to each other. The older gift bonds earned the high interest rates in the years past and they have aged enough for immediate cashout.
We’re buying each other a gift this year to keep undelivered in the gift box in addition to our normal purchases. If the interest rate is still good next year, we’ll buy normally and keep the gift in the gift box. If the interest rate isn’t good anymore, we’ll skip the purchase, deliver the gift, and cash out immediately.