You seem to be getting the right answers here. I would just have to add that if you are using a good release then it's possible you wouldn't have to replace a loop till you've put at least 10,000 shots through the bow. You ask about 500 shots? That's just about a month's worth of shooting and I only shoot half as much as I used to.
Giving an example, I use a rope release; Cascade model 8 to be precise. The rope serves the purpose of a string loop. The rope wraps around the string under the nock and connects to a hook--a very smooth hook. I have been using the same rope for at least 10 years and I probably avergae at least 150 shots per week. Just doing some very rough math that comes out to at least 75,000 shots. Still have no signs of needing replaced.
So if you are using a good release designed for loops you should be able to duplicate this. Of course, most caliper releases are not designed for loops.