Since this is HN, I'll instead say that if you don't have the guts, you're only lulling yourself into a false sense of security. AWS or not, your systems will fail.
By running the monkey, at least you can make it fail on a schedule that is convenient to you, instead of happening when you're drunk on a Saturday night (or whatever your vice of choice might be).
But remember: what's the difference between hacking and pentesting? Permission.
Increasing the amount of failures in order to increase the percentage of nice (not 3am) failures takes guts.