I have a large area that I have a helicopter flying over, and I’m using a distance texture map to generate dust when it gets close to the ground. Is it possible to create multiple grids, but use the same source on those grids so I only have to change one source at a time?
Or any hints for working with large areas?
Sure, yes - one source will work with many grids by default, unless you explicitly exclude it from the Scene Interaction rollout 
How are you planning on splitting the area between grids though? Mind that they will interact with one another and it might be better to exclude them from mutual interaction by changing to Include mode and picking only the source, emitter geometries and obstacles for each grid.