yes i've done many many studies and I find a lot of questions that if I answered honestly they wouldn't get a "representative" answer.

like on an alcoholic survey.
how many times a week do you drink
well say i put down 7, that probably looks like i'm a binge drinker, but actually it's a glass of wine a day.

I think they get around your problem because very few people should be in an unrepresentative week of their life. which shouldn't change the results too much

As well it is important that people support sex research. As there is a hell of a lot of misinformation about sex. Especially in the USA due to the government, we discuss some of their programs in class and they acutely lie on countless occasions