A good way to visualize both the near constancy of ridge production as preserved in the current inventory of oceanic crust is through the age grid of Müller et al. (1997) ( a beautiful collection of images are available at: www.ngdc.noaa.gov/mgg/fliers/96mgg04.html) that I have set in motion (Get the animation here).  The plate kinematic model used to create the animation is different from that used to create the grid, but to first order are quite comparable.  The production side of the equation can be viewed as the time variation in the area of new seafloor created at mid-cean ridges.  The animation shows that this terms does not vary.  The time variation in the destruction can be viewed as the cummulative increase in area of seafloor that has been subducted  and hence appears as black on the animation.

    Several other animations are included on this site to show various aspects of the kinematic history of the oceans and continents. Note that different reference frames are used for each of the animations. Top is Indo-Atlantic hotspot frame, middle- global mean paleomagnetic frame, and bottom-fixed west African frame.