I wonder if it would've felt more natural if the "part 2s" of the puzzles became separate days instead. (Still 12 days worth of puzzles, but spread out across 24 days, with maybe one extra, smaller, easier puzzle for the last day to relax)

Then the 24h between part1 and part2 could be spent trying to predict what part2 will be, or generalize the solution to see if you can handle whatever part2 throws at you. For instance the lanternfish ( https://adventofcode.com/2021/day/6 ) one would expect to just have a higher number, so if one solved part1 iteratively one could make an educated guess for a fast part2 solve.

I was thinking the same! This would be great , have a puzzle each other day. But i trust the organizers are going to do a great job and we will have fun either way.