I keep 3mos of living expenses in my Presidential Bank checking account earning 8%/yr tax-free. (Don’t go looking because you will not find it.)
How? Money is fungible. To a kid, a dollar from mother is worth the same as a dollar from father---he doesn't care who gives him the money.
Example. Assume your living expenses are $1K/mo, you keep 12mos of living expenses in checking, and all of your recurring bills are setup to pay by ABP (automatic bill payment) targeted to a 2% cashback CC. (The CC is paid by ABP targeted to your checking account.)
Each month you pay $1K of living expenses by CC, which earns $20 (=$1K x 2%) in cashback. In one year you will earn $240 (=$20 x 12) in cashback.
Since you keep $12K in checking, your return on that $12K is 2%/yr (=$240/$12K).
But if your reduce your checking balance to 3mos of living expenses, then the return on that $3K becomes 8%/yr (=$240/$3K).
Bottom line. You don't need to feel like you are leaving money on the table by not chasing bank teaser rates. Instead, get your return from ABP by CC.
This means you can keep your life simple by choosing banking relationships based on convenience, not teaser rates.
Disclosure. I opened the Presidential Bank checking account chasing their 4.05% APY teaser rate---long since gone. I keep it as my primary checking because I like the paper statements and decent phone customer support.
Keeping 3mos in checking means I don't (normally) need to worry about my checking balance until I reconcile next month's statements (banking, investing), and rebalance accounts.
I keep my savings in a local B&M CU that mails paper statements, and is part of the CU COOP network---easy nationwide access.
Redundancy is also good. I have a second ($0 balance, free) CU checking account, just as a CYA in case I'm ever locked out of my primary checking account. Both (primary + backup checking) accounts are linked to Vanguard so money is available within 2-business days (5-days max over a 3-day weekend).
And my mmkt (VMSXX) has checkwriting setup. But I've only every used it for gifts (graduation, wedding). It gives me an opening to talk to young folks about investing when they ask, "...what's a tax-exempt mmkt fund and how do I get one?"
d.r.a., not dr.a. | I'm a novice investor, you are forewarned.