DA, that's a loaded question and I'm sure you will receive various answers. IMO, It depends on the amount of N being appilied and time of year of applications. Normally if I want slow release I go for minimum of 50%. If your throwing a lb of N and only have 20slow, why bother you're still putting down 80% free urea what is the 20% going to compensate.
The Arena, the Field of Battle, the site where the fight actually takes place is our own heart and all of our Inner Man. The time of Battle is our whole life.