There is no need to regularly flash the newest images to your phone because the underlying system is built on pre-existing package managers for maintaining integrity. You can use the GUI applications (usually 'Software' or 'Discover') or because there is always a terminal nearby, these commands will help you stay updated with the latest available programs from your default selected repository.
To update all software, the following command will refresh the package cache, check for updates and install them:
$ sudo apt-get update && sudo apt-get upgrade
If some packages were held back, you can update them with:
$ sudo apt-get dist-upgrade
To update all packages under Arch-based distributions, the package manager pacman can be used:
$ sudo pacman -Syu
sudo pacman -Syu --cachedir /path/to/external can be used for a separate download location to improve installation speed, otherwise consider reading https://wiki.archlinux.org/index.php/Pacman#Configuration for further optimization.
If you encounter any errors during the update, you may have to update the Pacman mirrors. Under Manjaro this can be done using
sudo pacman-mirrors -f