First of all I would like to welcome you to HealingWell. I will try to answer your questions as best as I can, remember I am not a health care professional and I know others will come along and weigh in their opinions also.
Advair is a controller inhaler to be used every day. Xopenex as an inhaler is to be used as needed as you would any rescue inhaler. I also use Xopenex in my nebulizer. When your doctor puts you on Prednisone, it's when you really need it. My allergist tries to hold off as much as she can and tries the lower doses first. With extended use, Prednisone does put weight on and it usually around the middle of the body.
When you have been on it longer as I have, you can get the rounded face, the hump on your back at the top of your neck. My asthma is very severe though, and hopefully yours is not. So as to not scare you about these side effects, I take one injection monthly that cost $10,000 per year. You know your asthma is severe when your insurance company basically pays for most of it. I also have to use my nebulizer a lot. If your asthma is not this severe, I don't think you have to worry too much about the effects of the Prednisone getting as bad as mine. Take it only as you need it. But never hesitate to take it when you do need it, sometimes for asthmatics, Prednisone can mean the difference between life and death.