The problem I see is the total lack of scenery along that route. You get the industrial areas till you get past Chicago. Wisconsin, Minnesota may be OK but then you get to the "badlands." It's like riding across a moonscape. That will run from N Dakota to W Montana. W Montana starts to pick up some mountains. The Idaho panhandle is beautiful, but Spokane to about 50 miles E of Seattle is moonscape again. Crossing the Cascades then into Seattle will be OK.
So the 69 hours, I'm not sure where you will be during daylight hours, but you really will appreciate a room, with your own place to stretch out and relax. If you are planning on sitting up all the way, just fly and only be miserable for 8 hours, including your plane change connection time.