Nothing wrong with the verb "lengthen." Without CONTEXT who knows what the phrase means. The hits from Google refer to a Chevy Suburban truck (or SUV if you like).
Fair play, "lengthen" is proper . . . but, when would anyone ever say "Suburban-lengthen?" It sounds like one of those old AOL passwords, where they put a noun with a nonsensical verb, like "indigo-indemnify" and "lodestone-lathe" =))