It's MUCH WORSE than that, I'm afraid if we're going to count when Apple stops selling a particular model. I bought a Gen1 iPod Touch in early 2008 (it was released in September of 2007). It hasn't had ANY meaningful OS updates since June 2009, about 1.5 years after it was introduced (forget this BS 3 year number).
And don't forget how they charged iPod Touch users for the iOS 2.0 (and AGAIN for the 3.0) software update, which it seems like EVERYONE on here was saying they HAD to for accounting reasons; funny how they didn't charge me for the iOS 6.0 software update on my iPod Touch 4th Gen.... there goes that BS "theory".
The same is true of AppleTV Gen1. Yes, if you bought one when it was first released it had a few years of support. But by the time Gen2 was starting to sell, they never released any upgrades for it ever again (i.e. if you bought a Gen1 a few months before Gen2 suddenly came out, you got ZERO support).
The point is that Apple doesn't support products after they stop selling them. They stop supporting them a set time after they start selling them (or more like whenever it's convenient for them). Worse yet, they'll purposely leave features out for existing users to "encourage" them to buy a new one, even when the hardware is capable of supporting those features (just look at the iPhone features over the years).
But the usual crowd likes to throw around constant excuses why the richest company on Earth simply cannot afford to support their products for more than a couple of years while Microsoft has been supporting WindowsXP now with security updates for over a dozen years, whereas Apple won't do security updates for Snow Leopard anymore and it's barely two years since Lion came out (and never mind all the people that COULDN'T upgrade (whether they wanted to or not) to Snow Leopard and then again Lion and then again Mountain Lion. Too bad. They don't need any security, I guess. No wonder most corporations don't like Macs. Their server software isn't even backwards compatible with each other (i.e. you can't do software updates for older OS versions; too darn bad about that entire lab your company invested in that no longer is supported by Apple, etc.).
Yes, Apple is just too small a company to support their products for more than a couple of years.
Hell, in the case of iOS your warranty will last longer than your software support and the App store doesn't keep older software versions around for older devices like my Gen1 iPod Touch so it's effectively dead except for what I already bought for it and playing music.
Except they don't stop selling gas for your Subaru two years after it's released. Just try and get new software apps (even older versions that used to be available for a given model) once they stop supporting newer OS versions for your device.