That is correct. But there is a dark side to clowns and that is once sexually mature and mating, they will control about 25-30 gallons of tank space (unfortunate for those who keep them in a nano) and be aggressive towards fish that approach into their "virtual" territory. The other issue is that they will associate (what many people incorrectly call "hosting") with something. That could be a power head, piece of live rock, or sometimes a coral. If that is an "elephant ear" mushroom, they may get eaten, or if it is a goniopora, they may destroy the coral. For those that have a "nemo" issue for their kids, get a single clown and avoid much of these problems. Now don't get me wrong, a species tank with ONLY a pair of clownfish and a fancy colored carpet anemone (picked for that species) can be spectacular.
How would one know when their clowns get to this point? We have two that have been with us since at least Jan 2009. You can certainly tell which is female and which is male and they seem pretty content provided you do not disrupt much around them or their frogspawn coral. They were not wild about the starry blenny perching in the shade under the coral yesterday but they did not actively bite at him like the go after the husbands hand when he is scraping the glass around the coral.