It seems that the 1-2-3 rule is in decline on here. I used it (coupled with hydrometer readings to verify) for my first beer, a light bitter. Worked great, though I'm holding many of the bottles longer than 3 weeks.
For my second, a stout with OG ~ 1.063, I let it go for a couple weeks in primary at which point it had hit FG or close enough to my eye. I went to a secondary, not so much because I wanted to, but because I had to get it out of my bottling bucket.... it's been there 3 weeks now and I'm going to give it another before bottling. I might consider going longer, but I need the carboy empty and the house is warming up to higher temperatures than I'd really like and I don't want to deal with chilling this batch.
From what I've seen here, this length of fermentation is not at all unusual, and many would do all of it in primary.