Crosmando: Insomnia's "thing" was that it was a "scarcity" of discounted games, once they were all gone you couldn't get that discount again (until whenever they went on sale next I guess), so in that case it wouldn't have made sense.
PaterAlf: Exactly the same thing here. Except that the discounted games weren't limited in quantity, but in time.
And I don't want to know how many people would be pissed, who stayed up for hours to get a certain deal, if all the deals would return for the whole weekend.
The Insomnia promo did repeat though, if I recall correctly even several times. So if you missed a game the first time you still had a chance to buy it in the next round.
And if GOG were worried about people being pissed off, they should have done from the start what crosmando suggests here. I bet this promo has been a big success for GOG, and probably a bigger success than it would have been if they hadn't created all this buzz by making it a 24/7 event. But sadly creating a big buzz to sell more games and draw more people in isn't always the same as being fair and customer friendly, and that's the trait I value most in GOG. I want them to grow and be successful, but not at the expense of customer friendliness.