I believe the longer the tour the less route specific planning is required.

My wife and I started a 3 month, 7 country ride in Lisbon Portugal with only the first day planned. We planned a route out of Lisbon, but that changed when we talked to the ticket agent at the ferry terminal, who showed us a better route. We knew what cities and attractions we wanted to see, and and where we needed to be to catch the flight home. Our priorities changed frequently, sometimes daily. We knew the general route we wanted to take, and would plan specifics for one or two days at a time.

When we do our annual short tour with our daughters, we plan the route pretty carefully. However, I've never found a need for turn-by-turn cue sheets. Heck, on some routes you may not get off a road for several days. Heck, on one tour we roughly followed the same road for 74 days; sometimes we were on it, sometimes parallel to it. No smart phones or GPS, just maps we picked up as we entered a new state.

I realize that when there are time constraints, and a need to get from point A to B, it is hard to be so cavalier about route planning. However, try to leave some room for serendipity.