Most likely the CoF is more like 22 rounds in 22 minutes - 2 sighters + 20 record shots. That's a pretty standard string for mid-range F-class.
As mentioned above, the rules generally call for 1 minute per record round for mid-range, and 1.5 minutes per record round at long range.
It varies a little, and if it's a string with unlimited sighters, it's not uncommon to lump on an extra 5 minutes and let the shooter decide how many - or how few - sighters to take. But again, it varies. 25 minutes for 20 rds and unlimited sighters isn't uncommon for mid-range, but 30 minutes for 20 rds with unlimited sighters is pretty normal for 1000yds.
That said, it's somewhat unusual for a shooter to actually use all that time, unless they are waiting out a condition or having serious equipment issues. Putting 20 rds plus sighters down range in 5-7 minutes isn't uncommon. Yes, it's hard on barrels. One of the reasons that the dominant calibers in F-Open are a balance of accuracy, wind drift and barrel life. But at the end of the day, barrels are like the tires on a race car: consumable, and part of the price to play.
If you want longer barrel life, shoot FTR. Even then, (big) match winning accuracy in a 308 running Berger 20Xs is typically <2500 rds.