The body's natural tendency is not to urinate immediately. Even babies won't pee if they're in a stressful situation. That being said, it requires a signal from the brain to actually release the sphincter responsible for urination. And as we know, humans are fully capable of being trained.
Acknowledging that you're in diapers may be the only cue necessary to lose control. If you're so used to wetting in diapers without feeling guilt or panic or any sort of negative emotion (especially if coupled with a positive emotion), you will be accustomed to it, even to the point of complete lack of control...but only if you continue to encourage that behavior. If you find yourself going without so much as a signal, and you start to get nervous because of it, the problem will right itself and you'll get those warning signs back, because your body does everything it can to avoid an uncomfortable situation.
Now, the training goes on at an unconscious level, guided by conscious decisions. The subconscious is irrational and makes false generalizations sometimes. If you wear 24/7 for a long, long time, and become diaper-incontinent as a result, there is a possibility of actually becoming incontinent because you aren't in the habit of holding it in at all (to use the toilet.) In such a case, "immediate wetting" is the lesson you're teaching yourself even though you wanted "immediate wetting when in diapers." To ensure that you get the intended result, make sure that you make that distinction in your mind by wearing underwear and using the toilet now and then.
