[dayvan]

Find-and-replace exists.

Having a separate string for each level of progress also lets you do other kinds of customizations: you could have a rainbow progress bar, or put little bits of encouraging text to the right of the progress bar, like "Almost there!" at 90%.

Essentially, you're making one type of customization (i.e., changing the symbols) slightly easier, at the expense of making other types of customization harder.