Without knowing the particulars of the recipe...
If you pitched yeast 3 weeks ago and fermentation started as it should, then most assuredly fermentation is over. Have you taken any gravity readings to check the progress of the yeast?
Right now, you are just aging uncarbonated beer at room temperature on dormant yeast. Nothing wrong with that, until... at some point there is. Yeast autolysis is a risk, even if it's difficult to pinpoint when it becomes an issue. If your intention is to age the beer in hopes of improving flavor or round out flavors, I would rack the beer out of your primary fermenter and into a "secondary" fermenter...getting the wort off of the yeast. But, doing that opens up a whole other set of issues, the biggest being the risk of oxidizing your beer if your transfer is not a tip-top, airtight procedure.
So, I would just bottle now.