Sometimes it seems like Apple releases updates every other day. Because of this, I think it’s really common for people to get in the habit of ignoring updates, often for a long time.
In certain cases, it’s good to ignore an update for a while. When the upgrade is from version to version, I generally recommend that people hold off on installing for at least a couple of weeks (or even longer if your device is mission-critical). What I mean by "from version to version" is if you’re moving from iOS 13 to 14, say, or from macOS Catalina to macOS Big Sur. Before taking a step like that, you’ll definitely want to follow the instructions that Apple gives for what to do before you make the leap. (Those instructions are for upgrading to Catalina.)
That said, there are times when waiting for an extended amount of time to do an update is bad. Awfully bad. Bad enough that I'd shake my finger at you if I saw how far behind you were! Usually it's completely okay to do incremental updates shortly after they drop (like updating from 10.15.2 to 10.15.3), but when Apple releases specifically a security update, you'll want to install those as soon as you have time. This is because they can protect you against malicious code and other potential attack vectors. That's another reason why it's so important to keep your operating system from falling too far behind; Apple is still releasing security updates for macOS 10.13 High Sierra, which was released in 2017, but if your Mac is running a version older than that, you're no longer receiving those critical updates. This means that your computer will be at risk until you bite the bullet and upgrade.
(That's the icon for macOS Sierra. The red slash is my half-joking way of saying you shouldn't be running it anymore.)
So to sum up what I've said, do the smaller updates to your devices when you can; wait a while before installing new versions; and if you see a security update, install it as soon as possible. One more word of warning, though: If you depend on any apps that didn't come from Apple (like QuickBooks or Microsoft Office), you'll want to be positive that those programs will work with whatever software you're upgrading to. With macOS Catalina, for example, Apple dropped support for 32-bit apps, which means that many older versions of programs simply won't open at all. And there isn't an easy way to undo the upgrade! It's a real bummer to install a shiny new thing only to find that your most-needed application won't work afterward, so be sure to do some legwork ahead of time. Often doing a web search for something like "[name of program] [name of operating system] compatibility" will do the trick.
And please, please make sure you back up before doing any kind of update. Trust me, there's nothing like the cold chill of panic that runs through you when an update fails, your Mac won't boot, and you haven't backed up in six months. I don't want that feeling for any of you, ever!