From an "insurance" point of view, the protectors seem like a poor investment. If for $80 someone offered to replace my headlamp (parts only) if it ever in the future suffered a rock hit, I'd probably say no thanks, too expensive considering the risk.
But that's if I was fully rational. For some reason I did buy and install the dual-lock type on my RT - so far (20K mi.) it's never been touched except by bugs.