I have this defined in my /root/.bashrc (you need to have also the .bash_profile so it is triggered by the way).
alias up="emerge --keep-going --ask --update --newuse --deep world"
It means, update anything you need to but don't stop if one package fails.
As I have app-portage/eix installed, my update routine is :
Both with a nice feedback about what's new in the batch.