Back in 1982/83 when I was working on making the most accurate groundhog loads I could make for my M700 VS in .223 one of the powders I tried was BLC2 with the 45 grain bullets I was using. One of the many powders that fell by the wayside was BLC2. I stuck with IMR4198 for years.
When I moved to the Richmond, VA area in the spring of 1985 all my ammo/powder/primers/guns went into the attic.
Roll forward to about 2012 or so when I ran across a box of those reloads sitting on a shelf in the attic while looking for some other stuff. I put them in my pocket, finished what I was doing and came downstairs.
Next time I went to the range I took my vARmint rifle. An AR15 built as close to the bolt action M700 as I could build. 24" bull barrel, nice trigger, big scope and as close to a 1 turn in 12" barrel as I could find at the time (1 turn in 11", weird, I know, no idea what it was really made for). Those BLC2 rounds, about 30 years old by then and most of it in an attic with terrible heat/humidity in the summer and cold/humid in the winter) shot the best groups that vARmint rifle ever shot. I came home, cleaned the rifle, and my next trip to the gun store I bought more BLC2.
I'm sure, at some temperature, ammo can be damaged. So far, none of my ammo has been stored where the temperature/humidity is controlled and it has worked great.
One thing is for sure. The internet is a great place for people to pass on their experiences. And even what they hear of other's experience and very few people take the time/trouble to verify what they pass on.
Work in a big factory/office building? Ever notice that bad news, or bad rumors about someone get passed around at a rate/volume so far above the good news and good things about people by a rate it's impossible to measure? Yeah. Human nature I guess, to be more interested by bad news.
It probably is a good idea, if you load ammo up to store it away, to buy some surplus GI ammo cans and store you ammo in those. Easy to stack/store, protects the ammo (vs a standard box) from getting lost, damaged, wet if the roof leaks, etc.