In looking at your signature, you have been on cruise ships that are 2500'ish guests...
I have been on that size of ship in a previous life, before I found small ship sailings. The larger ship has a more diverse night life because of the size of the ship, but also because of the age demographics of the ship. (we are in the 40-60 age range)
Viking at capacity is only 930 guests and the average age is much higher than the ships you have sailed. Viking has designed an experience that meets the needs of the older crowd that wants more luxury and is not looking for disco dancing at night.
It is true that most of the streets roll up after the second show in the Star Theatre, but depending on what you are looking for, there are some options, but they are all fairly sedate.
As I mentioned earlier, we choose not to go to Torshaven as we find it rather enclosed and loud and we are not interested in dancing.
We have always gravitated to the Explorer Lounge after the show in the evening and we have generally always found that to be a relaxing end to our day. There will be either the guitar player or the piano player or a string duo there for a set or two.
As Clay Clayton said above, it also depends on the cruise itinerary as if it is shorter and really packed, folks are off to bed early. (We tend to book our excursions as early as we can)
When I think back to my time on larger ships, I fondly remember why I love Viking so much. It is because it does not have all the choices, noise, and confusion that I feel the larger ships have. On Viking the food is excellent, the service even "excellent-er", the ship is tastefully laid out in a Scandinavian calm colour pallet, and it just fits the level of luxury that we are looking for.
I hope you love Viking as much as we do.