Try to spend at least one weekend in Luxembourg, and make Ettelbruck your base. In 2014 our train from Bruges to Liege to Ettelbruck took about 5 hours.
Ettlebruck is a transportation hub in Luxembourg, and this little country has a marvelous public transportation system. When we were there it cost just 4 euros per person for a 24-hour pass that you could use on any train or bus within the country. Ettelbruck itself is a charming little town with some good restaurants (and even good gelato!). Find a place to stay that's convenient to the train/bus station, and then take some day trips.
You could go up to Clervaux, and see the Family of Man photographic exhibit, which has travelled the world and is now on permanent exhibition in a chateau there.
You can go to beautiful Vianden and climb up to the castle.
You can make a day trip into Luxembourg City.
And you must visit Diekirch for the most remarkable World War II museum. After the Battle of the Bulge, farmers in the area collected all the equipment/supplies left in their fields and stored them in their barns, until someone suggested combining them in a museum. There are actual jeeps, trucks, parachutes, weapons, with interesting life-size dioramas and fascinating letters and photos from Americans who fought there. You could easily spend hours there.
Luxembourg is a beautiful little country with friendly people. I hope you take the opportunity to spend some time there.