there are a lot of brushes made at 72dpi, the Adobe user forums are always griping at brush makers who don't make high res brushes
you have to check to see if the brush, tube, element, stock photo, clip art, whatever is print quality. Do this in Image>Resize and look at the Original Dimensions to see
I usually check brushes and tubes by making them larger than intended and stamping them. If they look horrible, then I either don't use them, or keep the really small.
Any other suggestions for checking the resolution of non-image elements like brushes and tubes? My way isn't very "scientific"