Phones can get lost or stolen, Firmware OTA updates can ruin your phone and you will be forced to reinstall OS again, the solution is writing passwords down in a book, either for BTT, exchanges or emails, this is the smartest move.
The best way to do something is to keep the password of this bitcointalk saved in youy phone and also have it offline because having it offline will make you login with any system you like to login with. I believe that many people in the forum is using offline storage of password of bitcointalk account.even some people do stores or save their email password in a document that is outside from the online documentation.