You can only buy $10k per person per year, but as a married couple, you could build up 100K in savings over 5 years, and even faster if you hold them in a trust.
One limitation of buying I Bonds is the annual purchase limit. Each person can buy a maximum of $10,000 per calendar year as the primary owner.
In addition, if you have a trust, you can buy another $10,000 per year under the name of the trust. A lawyer created a revocable living trust for us back in 2018. It was surprisingly easy when I opened an account for the trust at TreasuryDirect last month. It took only 15 minutes to open a new trust account and buy another $10,000 of I Bonds.
So it lets you double the amount you can buy.
The main benefit of cash recently is losing less value each day than stocks!
If you haven't already, look into Certificates of Deposit ("CD") at your local bank. They're FDIC insured (so if the bank goes under, you're covered, up to something like $250k) and you don't have to worry about losing the principal amount you put in. If you ever need to withdraw that money in case of an emergency, you only risk losing out on the interest. Instead of dumping a ton of money into a single CD, look into CD laddering wherein you setup multiple CDs that expire in 3 months, 6 months, etc or some other cadence that you're comfortable with.