I don't think it's a common term. I don't think "lengthed" is entirely a word.. kind of a made-up-on-the-spot word..

Sounds like it might have been used, to describe something being as long as a (Chevrolet) Suburban? Or else, trying to say that a certain area is as long as a suburb?? the second one seems unlikely..

I think this was really just one guy's phrase, and I think it sounds better as "suburban-length" .. but that's just me. =)