You know sometimes we make these things out to be way more touchy then they actually are. You put a dart frog in a viv with a moist substrate, food, and temps between 70-80 and it will probably do just fine for years and years. Wether it will breed or not who knows. I would avoid an all screen top thats all. humdidy should run from 70-95, dips or spikes a lil below that occasionaly arent likely to be much trouble, the occasional short temp dip or spike is ok too. i've had my heater screw up and my place get over 90 for an entire day, and my tank temps were already in the high 70s, frogs were all out and about, like it was the best day ever for them
though i doubt they would have enjoyed that spike if it lasted for more then a few hours.
smaller frogs like thumbs and pums are a little more touchy, just because of size alone they will heat up and cool down faster then a larger animal and loose moisture faster...so a more stable setup ensures their health. But frogs like azuerus and tincs are pretty bullet proof minus some real screw ups when putting together their enclosure. make sure you have your ff culturing down...nothing sucks like getting caught with frogs to feed and the only thing to do is overnight some ffs in less then ideal temps. so keep your pruduction steady...better to have extra then not enough.
If you've kept tree frogs and other amphibs you'll probably do fine.