I keep hearing how good Seasonic psu's are on here... well I bought one (Seasonic Focus PX 550) and it lasted 3 months, died, and now none of my case fans are spinning so it's probably killed some components too. My corsair vs550 lasted a few years without issue.
Don't believe everything you read.
Well, 1 failure (for you) is not necessarily indicative of a brand, or of all or even any products. With most things, you have a failure rate, and this can be applied to all pieces of hardware. Typically those failure rates are very low, like 0.0001 of a given product line (this is just an example).
Yes, you've had some bad luck with yours, but luckily it should still be covered for RMA. Maybe the replacement will work as you expect.
Seasonic often make great PSUs. They've had one or two that haven't been up to scratch for sure, but for the most part they are an excellent company offering strong components.
Although your VS may have been lucky enough to last in a some kind of rig, it's is of poor quality, and is only suitable for office machines. Never in a gaming machine.
As for the other brands, it's very much the same. Some are better than others. The good ones can make great PSUs and some not so good. Research is key, and knowing why you want the specific PSU for your build.