How long should bronchiolitis last in 3.5 month old. she's on albuterol and pulmicort nebulizers, and zantac (ranitidine) 3xday. could it be more serious?

Yes!: Bronchiolitis is often caused by a virus and usually lasts 7-10d. A cough or wheezing lasting longer should prompt investigation. Other causes are inhaled foreign body, reflux with aspiration, etc. It sounds like there may have been some suspicion of reflux with the Zantac (ranitidine) being used.

A month: The coughing and wheezing from bronchiolitis can last for a month. Typically it lasts about ten days, but it is not at all unusual to last 3 weeks or more. Follow up visits with your doctor weekly would probably be a good idea as other problems could occur such as an ear infection.