One particular issue I've always struggled with is game length. Back when I was doing the Ben Jordan games, I would write out a very basic design document outlining the story, locations, and to a point, puzzles (spoiler alert: I made most of it up as I went.) One thing I found was that no matter how extensive the game seemed on paper, when it came down to building it and playing through, it was always significantly shorter.
Now, one can blame this on the fact that the developer knows the game and can easily blast through it, but it's always a matter of concern. Granted, many classic adventures can be played through fairly quickly if you know all the puzzle solutions. In fact, a lot of the old classics more or less counted on the fact that the player would get stuck as a means of extending play time. I've seen people speed run Day of the Tentacle in less than 20 minutes, and most of the Sierra "Quest" games can be completed in a couple of hours.
So why is this an issue? Partly because there is a feeling of disappointment, after putting so much time and effort into something, that the result it yields is such a brief experience. I suppose the same can be said about movies, really. The cast and crew spend months preparing, filming, and editing, and in the end it's all distilled into a 1 1/2 to 2 hour film. In games, though, you tend to feel it more.
On the other hand, sometimes a story can be ruined by being too long. I know several people who complained they lost interest in Grand Theft Auto IV because the main story just kind of went on the back burner midway through. Sometimes a story just doesn't need a bunch of subplots. Straightforward can be good.
In any event, I managed to get through the prologue and first chapter of A Golden Wake in 20 minutes the other day. I was a bit concerned, but then I remembered there are still 3 more chapters to program, and on paper, they're longer than the first. If each of those takes me 20 minutes, then we're looking at a relatively decent sized end product.
If, however, the whole game takes me 20 minutes to get through, then I'm in trouble.