Manjaro is not just a rolling-release distribution; it is a curated rolling release. Barring any urgent security updates or equally urgent bug fixes to individual packages, updates are bundled together and issued on average about twice a month.
Packages go through rigorous testing via the Unstable and Testing branches before they end up in Manjaro Stable, whereby the Testing branch also follows the curated rolling-release update model.
Lastly, Manjaro’s Unstable branch is on par with Arch’s Stable branch, which means that a fair amount of testing has already been performed by the Arch developers upstream before it reaches us.