I prefer shutdown now gives me a feeling of power

I do ";" to definitely run the shutdown after the update process exits.

If you're able to successfully boot the machine afterwards is not your concern?

I do "|" so it updates and shuts down at the same time

And it's a login shell.

Yes, in this command one liner, the system should not power off when the update took too long.

Or is yes somehow supposed to take care of this?

No, yes is simply answering all questions asked during the update procedure (start upgrade, replace config files, restart services) with "yes".

The command after && runs only if the previous command returns non-error exit status (0), if pacman returns error the latter command won't be executed.

Additionally there's probably a configuration option for sudo for it to not time out, but it doesn't matter since you can just use systemctl reboot as a normal user to reboot your system (at least on Debian). If that's too long I recommend to add this to your .bashrc (if you use Bash): alias reb='systemctl reboot' or something similar.