I think it's helpful if one knows how fast one walks- it allows for constant refiguring of time of arrival, the day's overall walking time, time to lunch spot, etc.
For example, I know I walk on flat ground at roughly 3 m.p.h. (miles per hour, sorry metric types) at a saunter and 4 m.p.h. if I'm late for dinner. Knowing that info about yourself, you can make the big plans for the Camino, like you are doing now, but then also constantly adjust for the vicissitudes (terrain, weather, side trips, health, etc) you will inevitably encounter on the walk itself.
Go outside and walk for an hour with the full pack and see how far you get or walk a pre-measured distance and see how long it takes- then do the math for mph or kph. I think it would be good basic info to have.
PS: A.M.D.G.: I saw that a LOT on my high school test papers...