After it happened to me a few times that the footprint I got from an eagle library wasn't exactly what I thought it would be, I know make all components myself, which has removed that source of error. As an added bonus, you can more easily make small modifications to the foot print, to make them work better with the solder method you're going to use (e.g. make pads a bit longer if you hand solder, so you have room to place the iron tip.)
I learned not to implicitly trust 3rd party libraries (actually, not even the ones supplied with eagle, although they are better.) I found wrong descriptions, imprecisions or plain mistakes in the footprint layout every so often. Hence, double checking everything myself is required, and at that point, I might as well just do the whole thing myself.