Traveling in night is fine after chillas... but for the part of Jaglot to Skardu, the driver have to be very skilled and familiar with the local roads... a local is highly preferred...
Because if Allah forbid any small mishap happens in night... there for it is better of wasting a day... then wasting a life or so...
I have also managed few trips of 60-80 people in strength... and there is a 99% chance that a brand new bus can malfunction on a trip like this...
And you would not like to be in middle of nowhere in night... and mind it the night in those areas is very dark and terrifying (because of the massiveness of the mountain structures and the sound of rivers...) in that kind of situations...