Does he know about the setting to increase the grid size under Grid Snap / Grid options ?

You can increase the Grid sections: to something like 3000 or so to make the grid substantially larger. This setting is from the center to one edge of the grid, so that will create a grid 6000 squares across the full grid.

Is there some project that he's working on where a grid 6000 squares across is not large enough?

- Michael

Yes he knows that :)
I believe, it's more when you arrive to the "end" of the grid
And yes it's for some complex projects like cities or similar for video game