I got my first AR appox 2004. Reading here and other places I got the concept that I needed to have some spare firing pins.
I got one or two but have never needed them.
I'll admit I don't shot my ARs a lot. Looking around my gun bench area I cannot find them.
My question to you fellas is how many times have you broke an AR firing pin?

hopefully this won't seem an odd reply. Its a bit odd to focus solely on the firing pin.
I consider the following wear parts and have broken all of them...
bolt, extractor (also changed springs as well), gas rings (the thing I most often change), cam pin (I change this when it looks a bit worn and the retainer) and then the firing pin (normally doesn't break I just don't like the looks of it at the end, though I did have one fracture and actually it continued to run).
BUT at this point in the commercial market stocking the small parts seems a bit stupid. Just get a spare BCG with all the parts and when you lose one just swap and then you can diagnose your issues...
just IMO of course.

I have never seen one completely break, however I saw one with a chipped tip. Another AR15 owner said he had one with a chipped tip. Both rifles still fired. IIRC one owner stated that the chipped tip almost pierced a couple of primers.

Firing pins are wear parts. So are barrels, firing pin retaining pins, bolt rings, bolts, gas tubes, gas blocks, triggers. It all comes down to the number of rounds fired. My older firing pins have shown wear, in that the tip of the pin is a little shorter and a little more rounded than a new one.

I know guys who've put 20k rounds on pins, and the pins still function. One such guy in a training course had his trigger, gas block, and gas tube fail in separate days. One of my favorite lines from that course's head instructor was "It worked just fine....until it didn't".

I don't want to be "that guy", with parts failing halfway through a magazine. When my precision AR barrels no longer produce the precision I desire, I retire the barrel, bolt assembly, firing pin, gas tube, and gas block. This likely means about 5k rounds for me, which is probably fewer rounds than most shooters will switch out these components.

FWIW, I still have my older pins and bolts, kept in a used parts bin. They show noticeable wear, but they were still functional. It honestly doesn't make much sense to keep them around -- I have new barrels, bolts, pins, gas tubes in the basement for my next barrel retirements.

Never. And I’ve owner an AR for many years. Actually, two ARs.

I’ve fired my main AR, a Bushmaster a lot for casual plinking, training, qualifications and instructor schools. I’ve never seen a firing pin fail.

Now, I do have the small parts kits in my rifle bags in case any of the common items fail or I loose springs, etc.

I don't know how this matters in the scheme of things. I have had two broken firing pins. One completely sheared but worked, I found it in normal cleaning. One broke the tip. That's not many over the number of years I've been shooting AR's. I have however broken more than my share of lugs. On guns I run a lot that I want to feel like they will fun when I need them I just swap the whole bolt assmebly on a regular basis. Its what $250 for a complete high quality complete BCG. That's like less than an afternoon's worth of ammo. So bottom line to me, Firing pin spares are not the top of my list of spares. stock a bolt first, cam pin second and then you can branch out into the less fragile parts.

Spares are important, not only for replacing broken parts, but also for replacing parts that might be lost while the firearm is disassembled.

An AR-15 firing pin is much less likely to get lost during disassembly and cleaning than, say, the firing pin retaining pin, which is nothing more than a small cotter pin.

Springs of all types can go flying and never be found again, even though you know they are somewhere in the room- in the carpet or wherever. We've all experienced that.

Therefore, any small parts- springs, pins and the like- you should have in reserve, whether it's for your AR or a handgun or whatever. Loss, not breakage.

An inexpensive LPK (lower parts kit) set aside for your AR is peace of mind.

I've seen alot of cratered pins and one that lost a bunch of metal on one side and would fire intermittently that I still use for armorers classes with range days.

You arent likely to truly break one, lose it maybe but thankfully its easy to find. I'd have a spare or two though so its not a bad idea. If it makes you feel better the cratered ones still fire typically, they just have a depression in the tip. Still worth replacing but not a big deal in a range only fun gun.

BTW, flashlights are the number one tool i tell people to bring when we are detail stripping ARs. Its not that weird for something to take flight from the lower and its the best way to find the part.