Previews at Regal theaters typically last around 25 to 30 minutes. This includes about 12 minutes of ads/commercials before the actual trailers start, making the total preview time quite long compared to past standards. Some reports mention previews lasting as long as 30 minutes, especially before bigger films, with a combination of ads and trailers extending the wait before the movie begins

. In some cases, the previews and ads can cause the movie to start 20 to 30 minutes after the scheduled showtime, which has been a source of frustration for viewers. However, there are occasional variations where previews might be shorter, around 15-20 minutes, but the general trend at Regal is closer to the 25-30 minute range

. In summary, expect about 25 to 30 minutes of previews and ads before the main feature at Regal theaters.