Looks all good from here, all your sites URLs look clean and friendly for both search engines and users. Great!
Having unnecessary elements in your website URL's causes a number of indexation bugs and can detract from the users experience and natural link attraction processes. As a rule of thumb it would be best practice to establish a permanent link structure that is going to stay (henceforth permanent). Your URL architecture ought to be short, categorised and memorable for users. In other words "clean".