I worked with automotive glass for many years. There are longer lasting solutions out there. We even applied it as a standard feature for some door glass for a model in Japan. Expected it to last 1 year then the customer work get it reapplied at the dealer. That said they are coatings and will also have a limited life.
PPG has a product that last longer. As mentioned ya gotta start with a clean windshield. Offline I was told let it sit for 24 hours with getting wet and it will prolong the performance. I just look up this:
https://www.amazon.com/Aquapel-Glass-Treatment-Single-Applicators/dp/B004NFU300/ref=asc_df_B004NFU300/?tag=hyprod-20&linkCode=df0&hvadid=312168126179&hvpos=&hvnetw=g&hvrand=7114682588573615517&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9014871&hvtargid=pla-570727628621&psc=1&mcid=62ad3b31ef193c62bc6256f4b570b2b4&gclid=CjwKCAiA44OtBhAOEiwAj4gpOe7seNemaRv6z8RPYoLf 4SOy71Ngjp-eIa1mhYt7msZfQVGK6o2hIhoCklIQAvD_BwE