Humidity for White's Tree Frogs should be about 50% - 60% and their skin should be allowed to dry for a little bit everyday. This would be more similar to their australian home, where it's not as wet as say a rainforest in South America. Also it's been suggested that in constant high humidity and low temperature White's tend to be more brown. I can't verify this, but just a thought.
As for seasons, my frogs get the same care everyday throughout the year, I don't cycle them. I haven't seen this lead to any health deteriation and I haven't heard that it harms them.
Some links for you to browse:
treefrogland.mattewers.com/CareSheets/Whites.htm
allaboutfrogs.org/info/species/whites.html
media.animal.discovery.com/guides/reptiles/frogs/whitestreefrog.html
It seems that you'd either compromise the plants if you lowered the humidity for the frogs or you'd compromise the frogs if you kept the humidity high all the time for the plants. Some people get the beautiful poison dart frogs for their vivariums, or maybe some other tree frogs (waxy monkey?) would like the high humidity more than a White's would.
Good luck!
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0.1.0 Normal Leopard Gecko: Mala Ala
2.1.0 White's Tree Frogs: Wabo, Chabo, and Mushu
0.1.0 Bearded Dragon: Igor
5.0.0 Betas: Ghost, Fruity, Misty, Assasin, and Cobalt