Why update to newer versions - munin

Ppl tend to not update their software. There is a rule "If something works, do not touch it". But this rule is not true.
Lately I've update munin to version 2.0.19-1, and after checking performance of my kvm nodes I got really surprised. CPU usage for host which is mostly generating munin raports dropped from 23% to about 12%, which means that new version is 2 times faster!!!
All nice cpu usage on the graph is munin.