The spring sale already came and went so there wont be a spring insomnia sale. They could do an insomnia sale again in the future at any point in time if they want to but there's no way that we can predict for sure if or when they will as they don't pre-announce these things. I get the impression that they experimented with it and it worked for some value of work, they tweaked it and it improved but that ultimately perhaps it might have ran out of fuel and at the same time their mainstream seasonal promo format has improved quite a bit over time and likely produces more profit likely so perhaps they've shelved insomnia sales or put the brakes on them for a while.

don't really miss the format i have to admit

I did enjoy insomnia sales but nowadays I won't have time for it.

Insomnia sales were fun. Very entertaining.

Eh, I liked Insomnia sales better than other types of GOG promo. They made you work for the best deals and engage with the community.