WordPress updates get released quite often. New major versions come out every 100 days on average, but smaller updates appear much more often (around every 50 days if I remember correctly).
In short, it’s crucial for you to update as soon as a new version comes out.
Every new update comes with new improvements and new optimizations, thus making your site quicker (and safer, too).
Keep your plugins updated
The same thing goes for your plugins. Every new plugin update carries new improvements, not to mention security fixes.
So again, whenever you see a plugin update notification, act on it.