how long is online gre exam
1 Total Time: The computer-delivered GRE takes 3 hours and 45 minutes for the average student.  Experts recommend sitting for the GRE exam one year prior to entering graduate school. This allows for ample study time and the option to retake it if desired.
Once you take the exam, your scores will be available within 8-10 days. After that each time you order a report, ETS claims that it takes around 7-10 days to process it after payment. But it actually varies each time. It doesn't take more than 2-5 days after payment. At least in my case it got delivered within 2-5 days in more than one instance. During the GRE test you will choose which universities will get your scores.