Nor opti seal or OCW will give you huge durability on a daily driven car exposed to mixed weather. I found OCW will give 6-8 weeks and Opti seal will give you 8-12 weeks.
Both are great as drying aids. I tend to use Opti Seal more coz I find it easier to use and it works great on all surfaces.
Yes durability, slickness and performance will drop if you use it as a drying aid on a wet car but you should see durability between 4-6 weeks using it like this. You can still use it the "traditional way" with a foam applicator after you dry the car to add more slickness & shine. Durability will increase obviously and it wont take more than 5min to do the entire car.
Long story short....if you use it at least once a month your car will easily be protected till your next wash.
Its been my favorite drying aid for a couple of years now and Ive still got half of the bottle left....along with 2 full bottles still waiting in my garage, one of them being the old version.
Hope that clears out some things.