Ah, gotcha. Yeah, it's two separate questions. "Done fermenting" can mean "yeast has eaten all the sugars they're ever going to eat", or it can mean (more loosely) "yeast has finished 'cleaning up' -- processing intermediate compounds and floc'ing out". When you were talking about seeing a second ferment, I assumed you meant it in the first sense, just because I've never noticed the second sense having any visible signs. I've never waited for any particular indications to decide that a beer was ready to come off the yeast. How long to condition is just one of those things people do out of habit, based on past experience, or as tenets of their own particular brand of brewing religion.