30 minutes would be excessive. Keep in mind that the phone is unusable while it's rebooting, and that rebooting uses a nontrivial amount of power.
I think 3 days is actually perfect
But regardless of that.... why does it take a nontrivial amount of power?
But iPhones do not boot in 7 seconds either — it's closer to 40. At least that's what it took on my 16 Pro Max right now when I tested it.
I had to create a shortcut to actually trigger a reboot, as I couldn’t find a reboot option in settings. My iPhone 13 mini on iOS 17.7.1 took 29 seconds.