I'd take newer and higher miles vs lower miles and older any day. Highway miles are the easiest thing you can do with a vehicle and you already said this one is highway miles. If you like and its clean, go for it.
Wow, that is a crap load of miles. Guess they last. LOL.
My only suggestion to buying anything used is looking for heavy rust. If you live in the rust belt or thats where its from I would make sure it only has the usual surface rust and nothing more.