Love the setup! A 2012 machine is a classic.

To answer your question: VAM-Seek doesn't pre-render the entire 60 minutes. It only extracts frames for the visible grid (e.g., 24-48 thumbnails) using the browser's hardware acceleration via Canvas.

On older hardware, the bottleneck is usually the browser's video seeking speed, not the generation itself. Even on a 2012 desktop, it should populate the grid in a few seconds. If it takes longer... well, that might be your PC's way of asking for a retirement plan! ;)