Not necessarily. Unless you hit every square inch of it, you never know what can be found. We have a small park (about 1/2 block x 1/2 block) near the center of town, but in a residential area. It has been hunted probably thousands of times since the 1950s. I hunted it with my AT Pro and hit a silver: a dollar and two rosies. Just yesterday, I pulled a silver ring (3" down) from another local park that has also been hammered for decades. I find things is obscure places where others tend to not search.
My CTX-3030 will be here in Thursday and I will hunt both parks again in the coming weeks, to see what the AT Pro missed.