Regardless if you're doing small personal projects or doing commercial work, personally I don't find it too time consuming to just breakout the latest versions

Regardless if you're doing small personal projects or doing commercial work, personally I don't find it too time consuming to just breakout the latest versions of Safari, Chrome, and Firefox and do some local testing. Any experienced software developer will have some experience testing against those. I don't think you need to go out of your way to test against specific builds of those browsers, with maybe the exception of Safari and Mobile Safari since I have noticed standards-compliant differences over time with older iOS devices. That is to say, there isn't anything wrong with what Safari and Mobile Safari do, but the WHATWG living standards have changed over time just enough that older Apple devices may render web pages differently. Try not to just limit yourself to Chrome though. And if you're using vendor extensions, don't rely on them, just use them to pretty up from your baseline designs.