I would think they must (grow to accomodate girth ) My parents have a cat named Sox who, when we got him, was quite the lean, trim, athletic kitty. Then he became an indoor cat and WHOA! He got much .. ahem... wider. Anyway, I think his whiskers grew along with his tummy, because from looking at pictures they are longer now.

Both my cats also have leg whiskers - I think that's a pretty normal place. I love how the eyebrow whiskers get little curls at the tips on both my girls - too cute!