Is there such a thing as a "good first time double." or an "easy double"? I seriously doubt I'll ever do one one but ....
Up here ("here" being the PNW), there's the Seattle to Portland. 206 miles over two days, or all of it in one day. Mostly flat and not horrendously difficult... Unless some part of your body decides it's done and you're still 60 miles from the finish.