I found myself amending my commits quite often. I don't stash so much because I tend to forget I did so, especially when I want to save what I did before I leave or before a weekend, so I do a "draft" commit. Only thing is, when I amend the commit, it is still set to the original author date. Is there a (simple) way to update it when amending?

You can change the author date with the --date parameter to git commit. So, if you want to amend the last commit, and update its author date to the current date and time, you can do:

git commit --amend --date="$(date -R)"

(The -R parameter to date tells it to output the date in RFC 2822 format. This is one of the date formats understood by git commit.)