At MyAsthmaCentral.com I make an effort to answer your asthma questions. The following is a recent question and answer session I think you might find interesting.
Your question: Can I stop taking my asthma controller medicine. I take Symbicort and Singulair?
My humble answer: The answer to your question comes in three parts:
1. It generally takes about 2 weeks for the medicine in asthma controller meds to get into your system. So you can start taking them when you're sick, but you won't be getting the full effect.
2. The inhaled corticosteroid in Symbicort helps to control the chronic inflammation in your air passages. By doing this, by taking it every day, even if you get a cold or are exposed to your asthma triggers, your asthma should stay in control. Or, at the very least, easier to get back into control.
3. The inhaled corticosteroid also creates more receptor sites for your rescue medicine (such as Ventolin) to attach to. This makes it so when you use your rescue medicine it works better.
You can definitely gamble and stop using your asthma controller medicines, so long as you are aware of the risks. However, as a rule of thumb, I wouldn't stop taking your asthma controller medicines unless you have the permission of your physician.