Due to an injury, I ended up with a batch sitting in the primary for about 2 months and 1 week. I decided to bottle after purging some of the gas through the airlock and it smelled great (pressed on the lid and the airlock bubbled). I went ahead and bottled normally with 1 cup of dextrose for priming. The result was excellent. After a week of bottle conditioning, the carbonation was perfect. I used safale05 dry yeast in the beginning without pitching any more. I'd have to say the yeast may have just gone dormant or slowed down their metabolism. The temp of the fermentation was around 67 degrees. I would have to say that if you have some beer sitting in a primary for a few months, it may be salvagable. Like the saying goes - "If it smells good, bottle it!!!"