What's your idea of "stock up" and "a lot"? If you're really burning through 123's in large numbers, consider rechargeables, bigger batteries, etc. If "stock up" means relying on the supposed 10+ year shelf life of lithium batteries, it's not as trustworthy as some people seem to think. 123's can and do (not always) go stale on the shelf. Buying 1000's of them without a schedule for using them is not that great an idea.
Me, I gave up on off-brand batteries years ago and haven't regretted it. I use a dozen or so 123's a year and the price difference is maybe 50 cents a cell, so I consider the total extra expenditure to be affordable.
The whole concept of keeping tons of batteries around for emergencies is overrated anyway. If you look at the many real-life stories around this board about flashlight usage that happened during actual emergencies, the total battery consumption during them has not been that high, especially for small batteries like 123's. You should have some spare batteries and some low-powered long-running lights, and some higher powered lights for short-duration usage. If you expect to need high power and long duration, you wants a recharging system that you can power with a vehicle or generator or a deep-cycle SLA system etc. If you find yourself stocking up on enough batteries to run your lights for a 3 month outage but you don't also stock enough food and water for 3 months, your planning is confused.