We did the Star Wars VR on our last trip and loved it! The experience itself is less than 30 minutes, but I would budget an hour because there is queuing involved at multiple points throughout the registration and set up process.
After you purchase tickets (inside the building), you go back outside and wait outside the building (at the time of your reservation) to be allowed in to fill out your liability waiver. Then, after you fill out your waiver, you wait in line again to enter the pre-show room. After the pre-show, you wait in line again to get fitted for your gear. Once your gear is on, you have a short wait again for the party in front of you to finish and exit the VR room. Finally, you start your experience which probably lasts for about 15-20 minutes.