Herald of the moon took us 6 hours due to the many possibilities and long exploration in chapter 3. There are many fights that take a lot out of the party during their journey, intending to make the boss fight harder due to the lack of resources.
The exploration in chapters 1,2 gave the characters time to show their benevolent side and RP really well. The concern is that the boss fight at the end isn’t appropriately scaled due to the fact that the characters are expected to be whittled down by then.
Also a technical concern is: I feel that there is no significant detriment to the adventure if you let the shade coin run out.