Well, what does it hurt to be over-paranoid?
Personally, I've had too high humidity just from the ambient humidity in the house (incubator was dry) that caused one chick to hatch "sticky" and another to drown in the shell, and I'm terrified of having "shrink-wrapped" chicks/ducklings. I don't worry about temperature because my little Brinsea holds it perfectly (+/- two tenths of a degree is the biggest variance I had incubating a batch of Cochin eggs in it. I'm trying it with my duck eggs this year)
Better to be safe than sorry (and discouraged) - especially if you're using a homemade incubator.
Personally, I've had too high humidity just from the ambient humidity in the house (incubator was dry) that caused one chick to hatch "sticky" and another to drown in the shell, and I'm terrified of having "shrink-wrapped" chicks/ducklings. I don't worry about temperature because my little Brinsea holds it perfectly (+/- two tenths of a degree is the biggest variance I had incubating a batch of Cochin eggs in it. I'm trying it with my duck eggs this year)
Better to be safe than sorry (and discouraged) - especially if you're using a homemade incubator.