I did some reading just to refresh my memory and for preventative they suggest one to two sessions per day ..every day for as long as you want/need to continue.

The larger salt crystals are perfect - that is what you need.

Here is what one website says about what to expect:

If you are using the Inhaler for the general prevention of occasional respiratory problems, you will notice an improvement in a couple of days depending of your actual condition. Salt therapy activates your body's own defense mechanisms, which can help ward off seasonal microbial and/or allergen attacks. If you are using the Dry-Salt-Inhaler to treat a chronic respiratory disease, you should see some improvement in your symptoms 7 to 21 days after you start treatment.

I rally do hope that this provides you with a good measure or relief as it has for me. Keep me updated. If I learn any more tips I'll let you know.