Creating a course with 20 videos

Hi All, 

I am creating a course which contains 20 videos. The flash files are 3 to 5 mins in duration. The size of each file is 10 to 15 mb. I am concerned about the file size of the course files. Has any one worked with lot of videos in their courses? Can you please share your experiences, best practices and issues which you have come across. 

Thanks, Deepak