I live in Idaho and this is the first year I've tried a lighted nock, illegal until just last year. I bought some Nocturnals to try for this year.
The ones I used this year for archery elk I did not shoot more than one arrow at a spot when using them to keep from damaging them with another arrow.
This year when I shot an elk, the nock broke during the shot. It had a huge nock right kick on the way to the elk, which is why I'm convinced the nock broke during the shot. I would guess that the nock was shot somewhere between 50-80 times before I shot the elk. I am OCD about my bow tune and checking the bow tune afterwards showed that everything was still good.
The outer portion of the nock was completely gone when I recovered the arrow, which was stuck in the dirt behind where the elk had been standing, just the shank and light bulb remained. BH tip showed zero sign of hitting anything hard, still had a very sharp point. The arrow had gone between two ribs going in and a blade clipped a rib on the way out. Certainly no real hard impact.
Seems like a very brittle nock to me, very lucky I wasn't left with a blown up bow and poorly hit elk.
I am very unimpressed with Nocturnal nocks.
I have a set of Luminocks on the way to see if they're a bit more resilient, sure hope so. I do really like how visible a lighted nock is, but my experience sure doesn't leave me feeling very warm and fuzzy about them just yet.