I started to use Rain X upon recommendation. I applied two coats as recommended. Product lasts at least for six months. I do apply every six months even it is still working. I STRONGLY recommend this product. Driving while on hwy I do not need windshield wipers. In Edmonton, Alberta, Canada we are experiencing during winter temperatures reaching -45 degree C.

Rain X certainly does have a dramatic effect when you are driving in heavy rain.
The effect is amazing, no wipers on at 60/70 + and you can see.
Also keeps off the snow/salt from sticking to your screen.
Putting it on to side windows keeps the build up of rain stains to a bare minimum, also side mirrors benefit from an application as well.

I've been using this for 25 years. It's good on motorcycle visors too. It is best applied twice, and then use washer fluid Rain-X. It is very effective, but it is more expensive in the UK. You can buy it for less if you are in a French hypermarket.

Rain X leaves sreen crystal clean & clear. Lasts about one month depending on weather conditions and enables car to be driven without wipers in heavy rain above 40 mph. Rain drops are just blown from screen( based on products used on aircraft ?)