Question about high humidity

[the_flaxseed]

Ok, so I have a Boa BCI morph and she's doing great. Shedding, eating, pooping, growing etc. All the things that a young boa should be doing. My current question concerns her humidity.

I have her in a melamine enclosure that I bought from a petshop and I have her on coco coir chunk substrate. The substrate is slightly moist, but not wet by any means and her water dish is large-ish in that she can fit in it with some room and it not being cramped. Her temperatures are 78 on the cold side and 88 on the hot side. The issue I am having is that when I change her substrate, the humidity rises above 80% sometimes even approaching 90% for a couple days to a week before dropping to acceptable levels. I've also tried using dry substrate like aspen, with the issue being that humidity drops too low and I find myself constantly misting. I'm using two digital thermometers/hygrometers to measure both.

I've heard that high humidity can cause respiratory infections, but I've also seen people post that this is a myth and comes with other husbandry issues. What are your thoughts on high humidity? If it's a bad idea, how long can a snake withstand this issue without developing issues/discomfort? Best ways to reduce humidity without misting constantly.