The city of Vienna is called the "City of Culture" because (among other things) there are more than 100 museums in the city. As a consequence, it is very difficult (and very expensive) to visit all of them no matter how long you stay in the city. Fortunately, there is a special night, called the "Long Night of Museums", when you can visit many museums with just one ticket, from 6:00 pm to 1:00 am of the next day.
Nevertheless, it is impossible to visit every museum of the city for two main reasons. First, some museums in Vienna don't get involved into this event because they close at 5:00 pm. Second, there is not enough time in 7 hours to go to every museum, watch ALL their insides (otherwise, it would be a waste of time), and then go to the others.
Given the number of museums participating in the Long Night of Museums, the time needed to watch the insides of each museum, and the time that it will take to get from each museum to the others, you have to find the best tour to visit as many museums as you can during the Long Night of Museums.