How long does it take for tooth infection swelling to go down?

Antibiotics. If just on antibiotics you could expect 2-3 days, if you have had the tooth worked on and antibiotics it should be noticable sooner. See your dentist if you haven't.
Depends. The particular type of tooth infection, its cause and the treatment modalities will help to determine the efficacy of treatment. The swelling is a result of inflammation and when the inflammation is reduced there will be a gradual reduction in the swelling. If the treatment is appropriate it is likely that the swelling will be reduced within 5 to 7 days. If not, go back to your dentist.