This seems to be a first for GOG but yes, it seems to follow the same rules as you'd expect for a Steam sale. Don't buy anything till the last day, unless it's on a daily.

Unless you don't mind something popping up for cheaper of course.

That said, there's some sales that don't last throughout the whole sale, like the Mobysoft and Square Enix games, they end in a few weeks I think but they'll let us know 48 hours before that happens.

And yeah, as above. If *all* the sales turn out to be group sales like this I imagine 50% is the best we're gonna get if we're only after single titles rather than packs, unless you get lucky with what the other games are in the pack.