Comms, I'm still not understanding the need for replacement of the exact same flashlight model. We're not talking about something like a carry gun that requires practice time to get proficient. If the batteries are standard, then I don't understand why it matters if the flashlight itself is replaceable. If you buy a Fenix, maybe you have to buy a Walmart brand at the last minute before a trip...so what?
I think because I learned the hard way, that while having high quality, expensive/unique, hard to replace items make for cool gear porn, when it comes to survival, off the grid or in combat, that the lowest common denominator is usually best. I try to keep things simple.
This thread was not about replacing batteries, it was about finding a flashlight to carry in a EDC. Granted a flashlight is a flashlight and takes zero familiarization or training time but if you replace a small fenix with a larger Dorcy or maglight and it doesn't fit where you have reached for your Fenix 1000 times...Uncle Murphy loves opportunities like that to make it 'lost' in your pack or not in your pocket when you want it. Which is why I stand by my position that Fenix may be a great light and I wouldn't turn one down, but I advise people to be able to see the item in hand before buying and know where they probably can replace it when they need to, at the lowest common denominator, (i.e. Walmart, REI right away versus online and then paying maybe 50-100% of item price to get next day which still might be too late).
While switching from one flashlight to another seems so basic if batteries are the same, I can tell you that I have two CR123 flashlights. One runs 2 hours on new batteries, one runs 20 minutes. That's huge. I just bought a new headlamp that takes same AAA battery as others I own. Except the high setting drains my batteries 50% faster. Fenix makes a decent light and if you're used to it's batteries running for X amount of time, you can not rely on that same time for a different no name light that probably breaks easier or has inferior seals and fittings.
Now extrapolate the need to replace something like a fire starter at the last minute before a week long backpacking trip. You had an expensive but simple Blast Match, but could not get one at the last minute and had to replace with a cheap magnesium stick w/ mishmash that you have never tried before but you've seen them everywhere so why not, right.
Then what used to take a few seconds with a tried method to start a fire in the rain and wind, now takes significantly more time as you attempt to first just scrap the mishmash, then realize you have to scrap the block but again shortcut scrapping onto a collector, then trying to ignite this new contraption.
Keep moving up the ladder of gear. You rip that perfect online tarp with all the grommets you've had for 3 years and had to replace quickly with something from ACE hardware before a camping trip. What used to take a few moments to string up is now a foreign object b/c the grommets are not there, your hanging set up is different, then probably the constant need to readjust in adverse weather and a usually well rested night in the rain and wind was now sleepless and compounds your mental effectiveness the following day.
Trust me, just reading this response makes me seem like I have put way to effort to keep things simple. Maybe I have, but I always have what I or someone needs and I know I have 100% chance of it working they way I want.