Not a bad idea if you are worried about runaway inflation, but otherwise yields aren't great. There aren't any i-bonds issued in the past decade that are currently earning over 2%, which is less than a savings account or money market currently yields.
Yea, I don’t keep I-bonds for the yield, I keep them for the inflation protection and tax advantage. High yield CDs are fine too but the interest is taxed.
https://www.treasurydirect.gov/indiv/research/indepth/ibonds...