What Causes Intermittent Asthma Along With Bronchitis?

Question: Hi I am 53, generally healthy and active. However, after a bout with bronchitis a few years ago I have developed mild intermittent asthma. I really didnt enjoy the long term inhalers prescibed so I don't use them. I use the rescue inhalers when I start a mild attack and it works well. When the asthma gets rolling, the main trigger that worsens the the asthma is the post nasal drip. That creates a build up of mucus in the lungs and the cycle begins/worsens until I use the rescue inhaler. I've noticed taking Mucinex 12 hour (just plain guafnesin) once a day makes the PND go away and the asthma doesn't kick in. I like that it is not a steroid. Question 1) Do you see any reason that I can't take this daily for an extended period of time if it works with low/no side effects? (The label says "two weeks" to keep the manufacturer from legal issues is my guess! )
Question 2) Singulair is a non-steroidal treatment for asthma but it doesn't have very good reviews (claim it doesn't work, bad side effects etc..). Do you have a positive opinion on this drug for mild rhinitis/asthma? Or do you generally prescribe something different?

Hello- Thank you very much for your response. It was very helpful. However, I believe Singulair is Montelukast, not Loratidine. Generally, I am interested in a non-steroidal asthma treatment for my mild, intermittent asthma. I was thinking a combination of Mucinex and Montelukast could work well. I was presecribed Montekulast for a combination of the Asthma reduction through it's anti inflammatory properties and Rhinitis. I am just wondering what your thoughts are of that as a prescription? Or do you still recommend I try Allegra(Fexofenadine) along with the Mucinex? Thank you Dr. Bhavsar!