Hmm... Why would it die? Ask that 'someone' to give you the reason why the cactus would die. It doesn't need humidity, unless it's succulent. Usually cacti survive a long time without any water. If you want to transplant it though, you might need to let the root or the 'future' root dry up for about 2-3 weeks. After that you can successfully plant it, as it will develop a new root system. Otherwise they die from root rot. And do not water the cactus more than a tablespoon of water a week.