I try to make reusable applications of most everything I "know" that I'll be using more than once or twice. Permalinks and named URLs are pretty handy when you do not use the same URLs across different projects.
(EDIT: Added "Permalinks and" before "named URLs".)
This forces me to think about my URL design up front. Then, if I decided I want to change URLs later, I've got plenty of time to come to my senses and stop. Public URLs shouldn't change, so this can only ever be a problem during development where a quick `vcs diff` renders the problem practically moot.