The question is what part of the country do you live in and what is the average relative humility. I live in West Texas, it is normally dry so I don't need as much protection as someone living Flordia or Houston might. I use dessicant and about every six-eight months I put it in the oven for at 250 for an hour or so, it has worked well for many years.
I live in central Arizona so it is not too bad.
More precept than the Phoenix area though.
A friend was over and told me about someone he knows
in this area that had 30 guns virtually ruined in his safe.
I could not see that happening to me because I will be
opening my safe a lot.
I did just added a swamp cooler to my shop so humidity
will be higher in here.