Asthma - question about medication?

I've had asthma my whole life and am used to my near constant attacks. I am on two preventers and still need to take Ventolin at least three times a week. I'm a little worried about the constant medication, does anyone know if there are any side effects to using asthma preventers? I don't like using Prednisone as much as I'm having to either... Also does anyone have any pros/cons of using a nebuliser? I prefer to use my nebuliser when I'm at home because I find that it works a lot better than my inhaler with a spacer. My doctor is unconvinced saying it should be of equal or lesser effect. I'd appreciate any answers.