50/60 miles week in/ week out is a lot I think. We used to do a “mileage table” here where regular contributors reputed mileage done...2 to 3 thousand miles a year would be “top” range. (I put asterisks round “top”, because for most of us, it’s enjoyment that’s key.)
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I must point out that it's entirely possible to cover a few thousand miles in a year with enjoyment being the primary motivation. Mileage and enjoyment are not mutually exclusive.
I believe that pretty much all walking can be pleasurable - woods, hills, roads, fields, trails, urban, treadmill even - because enjoyment comes from a state of mind. But in addition to taking pleasure in ones surroundings, enjoyment can also come from meeting targets, and achievements such as walking further and/or faster in a day than ever before, or reaching previously unachieved summits. Strenuous days can be extremely enjoyable!
It's stating the obvious I know, but mileage is related to speed as well as to time spent walking. Two people might spend equal time enjoying the countryside, but if one averages double the speed of the other then they will clock up twice the distance. And, of course, the one who does twice the distance will probably see more of the enjoyable countryside!