An Apple Care Senior Advisor I spoke to on the phone on a different matter says, "If your "login" Keychain password is different from your computer Startup password (which uses the "system" Keychain") then you WILL be asked to enter your "login" Keychain password at least once each time you Start or Restart your computer. This is how it should be if your "login" Keychain password is different from your computer Startup password and you can't stop it from happening if your "login" Keychain password is different from your computer Startup password."
This all makes sense to me as it used to commonly happen it the early days of OS X as far back as 10.0 and is now back. This is the "login: Keychain and the "system" Keychain holding hands. This is a good (Apple security) thing.
If it happens more often it is probably some setting WE have control over, like the settings in Keychain that have to do with "Inactivity" and " Sleep", or some other setting WE have set. Mail can also ask for the "login" Password.
[] Lock after [5] minutes of inactivity.
[] Lock after sleeping.
I now only get one initial request at Startup after unchecking the above boxes in Keychain Access.
I hope this helps you all.