I'd say no it's not critical.
--- FROM THE HELP FILES ---
Use average BSP (mental ray for Maya) settings
When mental ray for Maya raytraces, it calculates the effects using an average of the depth and the average of the leaf size settings of the BSP.
To speed up subsequent renderings, you can render instead with the average settings (instead of your initial settings).
Find the averages in Maya's Output Window after you render the scene the first time (with Verbosity Level set to Progress Messages or above in Render > Render Current Frame > and Render > Batch Render > ), then change the settings in the Memory and Performance section.
That's all I've ever done but most of the time I never mess with it.
From a readers' Q and A column in TV GUIDE: "If we get involved in a nuclear war, would the electromagnetic pulses from exploding bombs damage my videotapes?"