Interesting insight, thanks for that. I suppose the success of that strategy depends on both the frequency with which CAPTCHAs are reused and the practicality of storing the encoded previous CAPTCHAs (considering the potential volume).

In my testing, reissuing the same CAPTCHA I had saved locally over and over again didn't make a difference to the duration in which it was solved. Now it could be that they throttle responses for pre-solved CAPTCHAs, but then of course they're also throttling their revenue stream. In this case, I'm more inclined to conclude that Antigate don't have a CAPTCHA reuse mechanism in place.