If you don’t refresh the ads or post a new ads daily, then your ad tends to get buried. In addition, if your ad just says the same thing, it’s familiar to the people who are currently looking at Craigslist. In other words, you should expect your marketing to give you better results on the first few days and then drop off significantly after the majority of the people who use Craigslist are exposed to it or your ad moves off of the first few pages.
When you market as an owner, you’ll be refreshing your ads and changing the copy frequently. As a test ad, it makes little sense to put that kind of effort in especially if you get a great response within the first few days. If you had a mediocre response, then you could try a marketing campaign that is more like the one you’d run the park with or switch to an alternative form type of marketing, like Facebook or Bandit Signs, to confirm the lack of demand.