The great thing about a large tank is that you never have to completely empty it! This assumes that the owner does the proper maintenance on a daily/weekly basis, and there isn't any sort of catastrophic failure (for example: the filter fails during a vacation and all the fish die).
By proper maintenance, I mean:
-Partial water changes (10-20% of the total volume weekly).
-A method for cleaning the "gunk" out from under the sand/substrate (weekly or monthly).
-Prompt removal of all uneaten food (every feeding).
-A filtration system adequate to the amount of waste the animals/plants produce.
-Appropriate testing of ammonia, pH etc, during the cycling period and occasionally thereafter.
Even a small tank CAN be managed in the same way. I have several 10-gallon tanks that I have not emptied or disassembled in the past 5 YEARS. (I moved 5 years ago, or they would have gone much longer!)
I would also mention that there are certain kinds of animals that cannot be managed this way. Turtles, for example, are just too messy to avoid total cleanouts, unless they are in really huge setups. An axolotl in a small tank may also need more cleaning than the procedures I listed above.