Here's why I ask this: Because it impacts the game's difficulty.
If you do say, a 1000 piece puzzle, The easiest way to do this is to split it into smaller puzzles. Split into 10 100 piece puzzles (sky, ground, house, whatever). It is more than 10 times easier to do a 100 piece puzzle than a 1000 piece puzzle.
And that's why Culture shock is fairly easy. You don't collect very many items. You don't have that many locations to try them in. In larger adventures there are many more combinations of things to use/explore/etc.
I'm not sure what the solution is - but if the episodes are tied together, in a way, that could help.
For example, you could start having things in your inventory that you don't even use in this particular episode. Culture shock had what - 5 locations? If the second one can add 5 more to that, and you have say, 10 locations to wander about in (with new things showing up in the previous locations),
then by the time you get to episode #5, & #6, then there's all sorts of stuff to try, and places to try them in.
If each game will be distinct though, with X locations each, then they will
all probably be about the same difficulty level. (unless you go into bizarro abstract mode with the puzzles, which isn't ideal)