We've just returned from an 1800 mile round trip to visit son in Bavaria. We had 12 days for the trip with 4 nights (3 days) with him. We saw some wonderful places but had to curtail our overambitious plans as too much driving AND sight-seeing is exhausting. Luckily the memories of places visited remains longer than the exhaustion. We found it best to stay at least a few nights in one place & making use of autobahns more than planned was a welcome releif to being stuck behind slow lorries on pretty routes. We also changed our plans to stay for 2 days (3 nghts) within striking distance of the ferry. We had discovered how enchanting north Luxembourg was so made that our final R & R destination.
We booked an Etap for the first night, other hotels via tripadvisor and a site giving reductions. It's hard judge standards - excellent or very quirky, but that's part of the experience. Do take a travel kettle - as many don't have hospitality trays. Having some control over food & drink is essential if you want a good cup of tea, cheap DIY breakfast or cuppasoup in an emergency!