We built some raised beds about 12 or so years ago, and they've done well for us other the years. When they started falling apart, we moved them and repurposed them. But they finally got so rotten that it was time to tear them out completely.
In this picture you can see what's left of the right-hand box. The left one is already torn out (it fell apart in my hands, no need for tools). The compost area is at the top of the picture, spilling over into the box zone. And though it's hard to see in the picture, the boxes are riddled with tree roots from the neighbor's yard, rendering them useless for planting..
And it's because of those roots that we're trying this type of raised bed:
It's 32" high, 21" deep, and 48" wide. It weighs way too much...
I still need to get some lag screws for the sides to help keep it together, but that's about it. We probably won't even bother treating the outside. It's made out of the same stuff as the original boxes, and those lasted more than a decade.