For how long does it take for a inner ear infection?

About 1-2 days. If the question is how long does it take for an ear infection to improve on medication, it takes about 24-48 hrs. After the start of antibiotics it may take 24-48 hrs to improve. Some ear infections will improve on their own but it may take longer.
Ear infection. There are 3 types of ear infections. The canal (otitis external, or swimmers ear, the are behind the drum (otitis media, the usual middle ear infection. Inner ear infection is unusual. I think you probably mean the middle ear infection. How long to get one? Or get better? Both vary, but usually it takes about 2 days of antibiotics to feel better, and finishing the Rx, to completely cure. .