Start with checkup of the validity, if your request is sensitive, since the amount of online fluctuate. Checker is not a condition, it is a recommendation, and lots of users work without a check, but in this case a number of error in your log would increase. Therefore, if you don’t want additional errors, perform a preliminary check.
Then read all the questions that have already been asked before by users of this service, you should understand the principle of proxy operation and according to that, adjust your software to get the best result of purchase or test.