Trollheart

There's no denying there are some fantastic instrumentals out there, written by premier progressive bands --- Genesis' "Unquiet slumbers for the sleepers in that quiet earth", from Wind and Wuthering, along with Hackett's gently understated "Horizons", from Foxtrot, and of course Alan Parson's wonderful "Sirius", to name but a few. But are prog instrumentals the pinnacle of the art? And if so, why? Is it because progressive rock is so much more complex, detailed and thoughtful than "normal" rock, or are there other reasons?
Or do you disagree?
And if you agree, what would be your favourite proggy instros?
Finally, is longer better, or is it the case that the more drawn-out a prog instrumental gets, the more boring it becomes? Or the better it becomes?
And will I ever stop asking daft questions?