Originally Posted by RM-MN
Of course there is potential harm. You might have a stuck fermentation and by bottling it might restart the ferment and get you a bunch of bottle bombs.
But, this could be true if you checked gravity also. In theory, there is no way of knowing that a fermentation is "stuck" and about to restart at some random point in time. In practice, this doesn't happen. If it does, there's a reason: change in temp, a blooming infection, new sugar added, etc.
I mean, think about it. If you take multiple readings, and they all show 1.019, is it stuck, or finished? The hydrometer can't answer that question. Go ahead and bottle it.
I'd prefer you to always check the hydrometer before bottling just to make sure it is in the expected range for final gravity.
Sure. That's what I do too. But as afar as waiting three or four weeks, then taking multiple grav readings, I say screw that. But I'm probably in the minority.
ETA: Just to be clear, we're talking about an extended primary here. If the question was about a 10 day old batch, I would definitely advise two readings.