As an escort I know that I get tested several times per year, even though I always practice safe sex with my clients and I never make exceptions. Even for regulars. Using protection is always a good thing but since it's not always 100% effective, it's important to make sure that proper precautions are being taken. If you're getting tested twice per year that's probably okay, especially if you're using protection. If you're not using protection though, you're putting yourself and the women you're with in risky situations. If you have concerns at any time, you should be getting tested right away before you have sex again. Otherwise, keep practicing safe sex and two times per year is probably a good number to go with. There's a lot going on our there so safety should always be a main priority.