Last week we finally saw the very first version of Windows 10 go through its complete lifecycle. if you have the original Windows 10 installed, it will reach “end of servicing” — no more security patches — in May. We’ve seen masses of sometimes-conflicting information about branches and servicing, as well as how and when Microsoft will cut off patches, but now the rubber has finally met the road.

Based on that death announcement, we can finally draw some conclusions about the longevity of Windows 10 versions — and, by implication, what you need to do in order to stay ahead of the bullet.

I’m not going to inundate you with talk of branches and builds, as-a-service and reimagining, betas and marketing blarney. Instead, I’m going to talk about Windows versions and how they are born and die.

Let’s start with some perspective.

, your last security patch, we’re assured, will appear on Jan. 10, 2023. That’s 3,728 days of security patches, or a little more than 10 years.

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It’s important to understand that all four of these versions of Win10 are completely separate, like Win7 and Win8 before them. You can’t mix and match. Microsoft gave them similar-sounding names, but they’re as different as dolphins and dodos. (The Long Term Servicing Branch is a different kettle of fish altogether — more about it at the end of this post.)

We can argue back and forth about whether it’s harder to move from WinXP to Win7, or 1507 to 1511, or 1607 to 1703, but there’s no question that upgrading involves significant change in the operating environment, and there’s a definite learning curve at each bump. The upgrades don’t come easy.

I hear three questions about Win10 all the time:

Q: If I upgrade to Win10 or buy a copy, which version do I get?

A: There’s no easy way to tell. Currently, if you perform a free upgrade from Win7 to Win10 (yes, the upgrade is still free, in spite of what you’ve read), you end up with 1607. If you buy a copy of Win10 (rare, but it does happen), you may get 1507 or 1511, but your first run through Windows Update will put you in the latest version of Win10.

Q: How long until my Win10 version bites the dust? Do I have to upgrade?

Microsoft has published a complex formula for calculating the end-of-life date for a specific version — several formulas, actually — and thrown them all away when dealing with 1507, the only Win10 version with an official end-of-life date.

Right now, my best estimate is that a particular version of Win10 will stop receiving security patches roughly 18 to 24 months after it’s released. That assumes Microsoft continues to push out new versions of Win10 every eight months or so, which is the current pace. It wouldn’t surprise me a bit if Microsoft changed its calculation method again. They last changed it last week. (Drop by if you want to discuss how I came up with that 18-to-24 estimate.)

Once your version of Win10 is declared dead, yes, you have to upgrade, if you want to continue to receive security patches.

Q: If I decide to go with Win10, which version is best?

InfoWorld’s Eric Knorr a couple of days ago.

In short, you need to choose a version of Win10 that’s been given the “Current Branch for Business” designation by Microsoft. If you want to wade through the , knock yourself out. But it all boils down to a simple (if embarrassing) fact: Microsoft releases new versions of Windows specifically, so they’ll get tested on tens (hundreds?) of millions of machines before they’re deemed ready for business — that’s the “Current Branch for Business” award. If you want to join the legions of unpaid beta testers, you can install the latest version of Win10. If you want to spare yourself some headache, stick to the CBB version.

Right now, the latest CBB version is 1607.

I’ve avoided discussing the Long Term Servicing Branch in this article for good reason. Microsoft doesn’t want you to install the LTSB version, unless you’re working with machines that have a specific purpose: ATMs, point-of-sale systems, medical equipment. If you put Office on a machine or run a browser, Microsoft specifically doesn’t want you to use LTSB on that machine. That should give you pause, if not shake you off entirely. LTSB versions of Win10 are sold differently from other versions. They don’t include Edge or access to the Windows Store.

At this point, there are two LTSB versions of Win10, called LTSB 2015 and LTSB 2016. You may be tempted to think of them as analogous to regular versions of Win10, but they’re not. Security patches for the LTSB versions of Win10 continue for 10 years after the product rolls out. You can’t use those security patches on other versions of Windows.

Questions — and discussion — continue on the .