Smoke detector batteries

I’m putting new smoke detectors in, and find it irritating that even with hard wiring they need batteries- can’t the have a big capacitor or a lithium coin cell for backup?

But anyway, smokes are supposed to last 10 years. Are there any batteries that last that long in one of them- we’re talking basically shelf life, correct:

Engergizer Ulimate: 20 year shelf life
Energizer Advanced: 12 year shelf life
Regular Alkaline- some say 10 year shelf life.

Whatabout all the Ultimates that my camera doesn’t think are good, but still test into the green on my tester?

There are wired detectors with 10 year lithium batteries.

I did see those, but they’re single sensor for almost the price of a dual sensor, and I need at least one combination carbon monoxide / photoelectric unit.

Or is having dual sensors a marketing ploy and not that important in real life?

There are unwired detectors with ten-year non-replaceable batteries, too. No link, but I’m pretty sure I saw them at Home Depot.