Continuously high humidity is sustainable by consequent spraying of demineralized water.
And in combination with moist bark, chips or mulch its more easy to maintain.
I use digital hygrometers for monitoring.
But my LRS says to high himidity causes scale problems.
My Teju and Rainbowboa both need 80% average for all I reckon.
A Burmese, Solomonboa and a Redtailboa should like a bit less.
But my Burmese lives in a long tank, so its possible to sustain a dry, a hot and wet, and a cool moist spot plus a pool.
So he has 60% as well as 90% spots.
Hes only to be found in hot and wet spots.
So..