I am considering using the same password for my Computer, Mobile and Password Manager.
The premise of the "password reusing is bad" rule is that if one website leak the password then all of your accounts on other websites are vulnerable.
But I don't see how it apply in that case. If somebody got access to any of my devices then it's almost game over for me because I am already logged in the critical services on my devices (gmail, bank, etc...).
The mitigation for that kind of situation is within each service by requesting 2FA for critical activities (send money, delete accounts etc..)
Using the same password would allow me to memorize one 15-20 random ASCII password , which I think would be way more secure than three different 8 ASCII password for example. Moreover, one single password allow me to change it more often.
Is this a good idea? What are the issues and threat of this approach? What would you do?