The problem with a screen top, is what you just said. They Aestivate alot. This can cause no mating, and further it can cause babies to die, babies do not aestivate as well.
Snail's mate and have their Eggs in the beginning of rainy season, that way when the baby's are born, it's still rainy and wet.
You letting them dry out and get wet, made them think it was the start of the rainy season. However the babies, won't Aestivate as well. So raising the clutch, or growing out snail's, it's better to have constantly high humidity and water. By not using a screen top, and misting daily if you do, or even multiple times.
My first clutch hatched in the Viv, I wasn't able to seperate, and I allowed the snail's to dry. Out of 100+ babies, 3 survived that dry out. I thought they all aestivated, and the babies did try, only 3 were successful.
There is also the growth aspect. Snail's do not grow during Aestivation. They go into a frozen state, where their bodies do Litteraly nothing. That's the opposite of what you want in a growing snail. Remember a baby takes 6-8 months to reach adulthood in a purely rainy environment. So if you allow water, half the time and dry the other half, take that 6-8 and make it 12-16, take the 3-4, it takes to become feeding size and double it as well.
I do think having a screen top, or a fan system is helpful to force Aestivation. If you want to. IE keep humidity up 100% till grown to feeding size, then Aestivate them all. Then gently pull some off and wake them up to feed Gutload before feeding to the Cham, it can extend the clutches usuablity.
If you want to raise naturally or have something that will eat adults, high humidity is best, as is a plastic lid. This also provides more surface area, so you can house more snail's, before they start killing each other off.