I don't know specifically about green tree frogs, but when reading about my gray tree frogs (and I know with a lot of other breeds) you have to do a type of season cycling to get them to breed. You have to create a cooling period followed by a warmer moist period in order to stimulate their breeding.

So I don't think that it is something that you really need to be concerned about. There are people here who know WAY more about breeding than I do though, so hopefully they can chime in!