I realise pop-ups can be annoying, BUT we are undertaking the research (in the UK and USA) to get a better understanding of our readers/users, what products they own, what they're looking to buy and so on. This will give us invaluable feedback to help make the magazine and website better. Given that this website is completely free to use, I don't think it's imposing too much to ask people to fill in a questionnaire - in fact, hundreds have already done so.
As for the frequency, it shouldn't reappear once you've completed it but I'll check with the tech team how that works exactly. It's due to end tomorrow anyway.