A huge show i was an assistant on in saskatchewan

Being a Pyro professional yourself - a show that keeps your own interest will certainly give clients the "wow" factor. The high-budget shows switch music, effects (and general theme) for a reason - too keep it interesting.

That being said, I suspect many of us on these boards don't get those opportunities too often. In effect, you've answered your question by stating " The event and customer...dictate how long the show should be".

Sometimes we have to "adjust" the clients expectations to match the budget,site requirements, and the almighty-hand of the respective AHJ.

You could set-up mines, fountains, etc. for some filler...yet find it ineffective due to the 80 foot wall of tree's between your display and the crowd.

Inherently, you have to ask yourself that question for EVERY display you design; that's what makes each show unique, a representation of your display company, and this industry so much fun!

When you stop asking yourself that question - it's time to move on! ;P

To kind of reply to fireworks4u's request...
Not being a professional, but just a Canada Day junkie, I enjoyed the show and would have loved to experience it in person. It is very hard to justify traveling for a couple of hours for 18 minutes as I am hoping to do to get to Niagara falls this weekend or next.

That being said...
It did start to feel a bit long at times. It was usually during lower fill effects, some of which seemed lost in the distance. Could the budget spent on some of those have been put into higher effects which would have also cut a few minutes from the show? The effect at 9:15 seemed especially budget wasteful and more suited for a shorter viewing range 1.4 event.
It felt like there were 2 "act finales" and then the grand finale?
I kind of liked this although for me it confused/distracted from the massive ending by making me wonder if it was actually over. Only the run time clock let me know. I didn't hear any crowd applause at the end, which I even get at the end of my $1000 neighbourhood show that takes me almost as long to mostly hand fire 1 at a time with a remote fire of a 12 cake finale.
I am wondering if the crowd also wondered if it was done. I assume the shots at the end were to signal the end? I prefer massive sky filling blasts for the end with no crackle for maximum final wow factor.(especially after 30 minutes)

Over all though, as I said at the beginning, I bloody well wish I was there!

I hope that this input is helpful, and thanks for the post.