I actually prefer my games to be shorter rather than longer, as far as single playthroughs are concerned. I'll take a good 5 hour game over a good 80 hour game, all things equal. I also thought Portal 2 went on for a little too long. There was some filler near the end that just dragged it out.
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"When I was a young man, I had liberty, but I did not see it. I had time, but I did not know it."