Bank Vaults and temperature controlled rooms, sounds like something from the Vatican.
In all Seriousness, are you storing 10k+ cards?
I just keep mine safe from Accidents like water, Fire, Theft and direct sunlight. Anything high end is in safe deposit boxes, ive never asked about temperature, I doubt they are cooking them
I’ve always wondered how much desiccants were actually necessary myself. I’ve owned slabs for almost 10 years now and never used them. I live in FL too now which is humid, but my apartment usually isn’t. I have slabs stored both in wall display cases and in pelican cases.
I use a FORSPARK dry cabinet to control humidity and also store in places without large temperature swings.
The bank I use has completely temperature controlled vaults 24/7. Thermal and other stats are monitored by the security firm they use. Therefore, humidity is not a huge issue, but I put some extra silica inside just to be safe. Downside is the tedious process to get to the vault though, which can partly be softened by having some high res scans of your cards/items 
Be sure to understand their access mechanisms. Some are even more tedious than others. Also ask what kind of insurance they provide (if any, mine for example does not insure anything). It can also be interesting to know if they do a stocktaking of some sorts.
I’ve never seen card damage happen from ambient temperature. I’ve seen mold in cases, but if there is mold I think you’ve got bigger problems in your house than just with your cards. Like a significant water leak.
If they’re in long term storage like a storage unit or non-air conditioned part of the house you can always seal them inside ziplock bags and then inside a tupperware. That’s what I’ve done historically with no issues so far (15+ years, knock on wood).
These are pretty neat and really not that expensive. I definitely would not have thought to look in the photography domain for a humidity-controlled cabinet. Awhile back I was looking at something like this but the sites I was finding were aimed at scientific/industrial use, and were usually ~$1000.
After a bit of research I ended up going with a bluetooth hygrometer that connects to a phone app (SensorPush) and a bunch of cheap silica packets. It’s amazing how effective the packets are! 3 packets in a ziploc bag will bring the humidity down to 25~% and keep it there for weeks. I know 30~% is a bit better but I have noticed that card savers are a moisture trap and if I’m not strict with the humidity moisture does form around the corners of the cards inside the card saver (even though they’re in penny sleeves).