2 year old on antibiotics? How long before taking her back in?

My daughter was given antibiotics for a sinus infection on the 8th. Amoxicillian. She is still having a large amount of mucous, and now has a yucky sounding cough. I'm thinking that she's getting Bronchitis also. In the past when the kids got bronchitis they were given amoxicillian also. So basically what I'm asking is how long should I wait before deciding that these meds aren't working? I was planning on giving it until Monday.