Assuming a single golfer (with no players in front of him/her) most golf courses require 4-5 miles walking which at a moderate pace takes up 80-100 minutes (1:30) of the golfing experience. 90 shots (close to the average golfer) should take no more than 20 seconds each, adding 30 minutes. BINGO! 2 hours for one average golfer playing alone. I've done this several times at Dornoch (most recently at age 60), and the numbers match the model.
The gold standard for fast golf was 35-40 years go, when Steve Scott (world class middle distance runner) played a round under 30 minutes, carrying two clubs and holing out, shooting 95.
Fast backwards. In the summers of 1981-1990 I played Dornoch regularly in a July fortnight with a moveable feast of fellow golfers, with handicaps from 5-20, age 40-60. We booked 3-4 tee times every day, first 4-balls, arriving on the 1st tee at 9:40 disheveled but eager, threw balls up on the air to select partners, and then teed off and played. The length of the average round was under 3 hours. If we were out of the hole we picked up. If one hit a ball into the grunge he looked for a minute and then walked forward. We talked, but as we walked, not standing on the tee. As we walked towards our ball, we focused on the lie and angle of the shot, and chose our club, hit it and then walked on. 10 years of this schooling taught me more about GCA than any pontifications, such as this.
Therefore, what? Well the first time you play a course, just enjoy and save architectural thoughts for the 19th hole. If you are not in a "one and done" mode, play or walk the course again--that evening or the next day. Spend some free time thinking about why you liked or did not the course or some of its holes, and most importantly, why. Keep a notebook. Enjoy!
Rich