It can vary. There are two different processing options that are provided by the USCIS, regular processing, and premium processing. If an applicant uses the regular processing route the processing times can be anywhere from 2 months to 3 months, this varies between service centers. If an applicant uses premium processing it is a guarantee that the application will be processed within 15days, however, there is an additional $1225 filing fee paid to the USCIS. In some cases, the USCIS request additional evidence which causes the time to reset. With that being said, Premium processing can take anywhere from 15 to 40 days.