We have only been using it a short time but I do notice this - it holds humidity EXTREMELY well. For example, the humidity right now in here is 23%. In all enclosures we have maintained humidity levels of 80% (give or take per enclosure - that's the average) for the past 3 days - without having to spray mist since switching to moss! We use natural daylight for light in the room where they are and we have glass I had cut with handles drilled through to cover the screen tops which I made removable if we need to. These also help hold the humidity levels.
Our vet, who we are fortunate enough to have is also the herp vet for all the reptiles at the Arizona Sonora Desert Museum here in Tucson. He knows his stuff. He's actually the one that reccomended it to us as he said he knows of quite a few herpers around here that can attest to postitive results with it. With the Repti here in the desert we just struggled to keep humidity levels up all the time.
I also wanted to kow if it made a difference where we bought and he said no so long as it was labeled as the only ingredient being peat moss. It cannot contain any other additives - good example of this is MiracleGro peat moss - it has MiracleGro plant food mixed in with the moss. Not good.
We got 2.2 cubic feet compressed at Lowes for $9 and change. It's pure Canadian Sphagnum Peat Moss directly out of Canada. No bugs and the thing we notice is that the boys seem to like it better than our old Repti-Bark moss combination we were using. No lie. Our boa Mr Biggs used to spend all of his time slumped up and around the water bowl but since we put him in the new setup with the pure moss - he now lies fully streched across the tank and has continued to do so since putting him in there. Our RTB seems to like it better also as he loves to bury under the substrate and we now rarely see "Gopher" at all except for his snout protruding out. Oh well, as long as he is happy. (He's prone to regurg so this substrate makes him want to bury which also brings him to his low wattage UTH for belly heat). I have nothing against Rept-Bark, we used it since we had our original setups.
But to sum it up, here's why wer'e sold on sphagnum peat moss (in order);
1. Hold humidity levels EXTREMLEY well.
2. Judging from our snakes reactions, they seem to be more comfortable on it.
3. Cost - for what you get it's a fraction of what we used to spend.
4. Upon "turning" the peat moss substrate in the enclosure, it will dry out the top layers fairly quickly which is nice if you want to avoid possible mold issues. (We have never had mold or fungus issues).
5. Less need to spray the enclosure.
Hope this helps. Lemmie know if anybody else out there would like more info.
Jeff in Tucson AZ