When we were planning our Dales Way walk, we found several journals, diaries, and planning articles from various sources --
One thing we noted, when we finally actually walked the path, is that there are minor discrepancies between distances actually walked (or distances shown on new signposts or in new guidebooks) and distances stated on some websites. I don't know if it's due to recent changes/diversions along the path, or if the path has been re-surveyed in recent years (with better equipment, perhaps?).
For example, the distance from Ilkley to Bowness is stated (on varying websites) to be between about 75 and 84 miles, while the distance on the signpost in Ilkley shows 82 miles. Distances between Ilkley and Burnsall are stated as anywhere between 12 and 14 miles, and distances between Sedbergh and Burnsall are stated as anywhere between 15 and 17 miles. (The path winds around Sedbergh a bit, so that could explain some of the variation). None of these variations are terribly troubling, but it just might be wise to be prepared to walk a little more distance, (or a little less distance, even) than you might have originally planned.