How did Otto Perry do it?

I'm constantly astounded each time I visit the Denver Public Library's Otto Perry photo collection. Even when I'm looking for photos of eastern and Canadian roads, I look there first, due to the collection's breadth.
And I often wonder how he did it, being a full time mail carrier? I realize train connections were much better then, but traveling still took lots of time anc cost money. When he drove his old Ford, the roads were generally horrible, so that took lots of time also.
How much vacation did mailmen have back then? I doubt it was over two weeks per year, but he sure covered a lot of ground and amassed an amazing collection of negatives. I'd like to know how he did it..