I commend you on your diligence this time around - it's good that you care.
How often really depends on how many occupants and how big the terrarium is. It also depends somewhat on what substrate you use. I tend to use simple terraria. I have a base of top soil or coconut fibre - top soil is safer for longer. I usually have a few potted plants that I leave in the pots, just making spaces in the substrate for the pots - leaving them in the pots makes them easier to remove at cleaning time. In the small size tall-type exoterra or zilla terrariums with two frogs I would clean them out every month or so - if you do spot cleanings of poop during that time then you could probably get away with leaving it a few weeks longer. A larger terrarium for the same number of frogs would require less frequent cleaning, but bigger, messier species like White's Dumpy Treefrogs would need cleaning sooner.
Breaking down, cleaning and renewing a terrarium like I just described takes less than an hour because of how simple it is. you should wipe the surfaces in the tank, including any cork backing and such, fake plants, etc. I just use a damp cloth and give it a good wipe but some people use dilute detergent - if you do so, make sure you really wipe well afterwards with a water-soaked cloth to ensure you remove any detergent residue because this could harm your frogs.
All the best,
-John