I would have done it if I could - the Dunedin survey which was similar design is fascinating and has given some really important information about child development. That said, people who are involved in these studies should demonstrate professionalism. They're probably undergrad students earning some money on the side, but it's really important they try to build rapport with you as the rapport can actually effect the validity of the study (e.g. if you're p'ed off with them, the answers you'll give will be of different quality to if you got on well with them). If you're signed up for the long haul, I'd drop them a note with objective information about what the issue was. And I would just say (yes, wearing my researcher hat) that while the questions might seem pointless and repetitive, it's likely that there are subtleties in the question that will help them in their analysis and making sure that their conclusions are right. But I totally know how you feel