Feature request: option of warning about missing frames once per session, or only on import

If I'm comping together a 3D render I will often be waiting for the frames to arrive while still working in AE. A handy technique is to render the first and last frames to create a placeholder, then the 3d render can work in the background filling in the missing frames while I do the compositing.

This creates the problem that AE will warn about the missign frames every time a new frame is rendered. You can disable this by turning off the warning in preferences, but that means you won't be told that your image sequence is missing a frame or two next time you import one, which is even worse.

A good solution would be to make the warning about missing frames appear only when you import a sequence, when you open / save a project with missing frames, or when you render.