An intersting conversation. Open moor trails are few and far between away from Dartmoor but open moor series (such as the Ten Toors series or Somewhere on Dartmoor) are more common. These take more than a day to complete or if possible in a day are a challenge to do so and need car assistance. In mountain areas where more there is more ascent involved than on Dartmoor, long trails would involve alot of vertical ascent in a day and be exhausting.
I must admit that I enjoy these more and they seem to come in various forms- some have a letter= a number solition to where the final bonus is but others ask other things of the cacher. Gwyddno’s Mountain Challenge in North Wales has 15 mountain general knowledge questions to solve at home. I recommend this series- the final is beautifully placed- there are 3-4 ways to get to the cache- all but one are a 5 for terrain and the other is a 4.5. But it does not require climbing skills or equipment.
The big Granddaddy of these series is the SWMCC series in South Wales- have a look at my log for SWMCC 30 for my statistics for the series. From memory 6000m of ascent and over 100km horizontal travel on foot.