In the world of RPGs, length can be an intimidating statistic. Few games in the genre can be finished in a day, and the time commitment required for some of them (Persona 3 and 4 come to mind) is intimidating. Many people have time crunches every day that make them leery of starting very long games, which is perfectly understandable. Often the games themselves seem to run out of gas before finishing, which makes their time demands insulting. Is there a point beyond which no RPG can sustain itself in terms of time commitment?
Some people can probably come up with a definite answer to this question, but I'll have to waffle and say 'it depends.' Roget Ebert brings up strong feelings among video game players, but I'll paraphrase something he said anyway: "A good game is never too long, and a bad game is never too short." Like most rules, there are doubtless exceptions to this one, but in general I think it holds true.
I can come up with numerous examples of games that I wanted to go on longer because I was enjoying them greatly, but Dragon Force serves to illustrate the point. Each of the 8 storylines can be completed in around 30 hours, but I've definitely sunk far more time into the game than 240 hours because I didn't want to rush things. Yes, Dragon Force's story is reasonably entertaining, but I never purposefully drag out a game unless I enjoy the combat, with both Dragon Force games providing that. It's the reason I occasionally pop one back into my Saturn for a little fun even after all the hours I've spent with it.
For a game that couldn't end soon enough... while I'd like to whip out Final Fantasy: Mystic Quest, instead Lunar: Dragon Song will get another lambasting. I don't play primarily for story, but Jian was an unlikable protagonist, and Ubisoft didn't do a very good job with the translation. The events of the game (particularly at the end) make no sense within the overall Lunar canon, and the pacing is awful. I've dealt with unpleasant stories before though, and Dragon Song's list of problems is even bigger when its actual playing mechanisms are considered. I did review it, in case anyone wants to see a more detailed analysis of the horrible problems. Suffice it to say twenty minutes was too much time spent with this.
My perspective is that of someone who doesn't mind not advancing the plot for long periods to drag out playing time, and I realize this is not what everyone does. The principle of not minding a game being good enough to sustain interest hopefully applies to everyone, though. Any game that can avoid repetition enough to justify being very long is fine with me.