The last time I bought one of these was 3 years ago, and it las5 at least a year before the light-sheath started to crack and fall apart.
This new one lasted a week before the light-sheath started to crack, and one of the pieces of clear plastic that transfers the light around the neck has come out on one side. The light and the other side still work, but I can't get the loose one back in. It seems that the position holes have some imperfections that prevent the light-bar from being inserted properly.
I did recommend this product to multiple people at the dog oval in my small town (before it started to come apart). And I've seen at least one other person with one since then. So it is an excellent product, and it fits my dog really well, which is great because he's an oddly shaped mutt, but I think some quality control measures might need to be re-examined.