I agree, but there's a tradeoff which is that not every language/data format supports duration types:

Ruby:

    config = SOML.load_file('config.soml', symbolize_names: true)
    config[:timeout] # what are the units? uses SOML::Duration non-Ruby type

Even worse if you ever convert to/from JSON. My opinion is that config files should be as dumb and simple as possible. If you want humans to be able to read/write fancy stuff like "72h" for config, build a UI layer for the human to use in front of the config. Then they can click a little calendar icon to select the date. The backing config uses dumb iso 8601 string instead of a magical date type baked into the config language.