Don't ask questions for which you already know the answer
I was recently completing an online form to submit a proposal for speaking at a conference. I had to log in to the system for it to recognize me (which it did). One of the first questions it asked me was "Have you ever spoken at this conference before?"
So the system knows who I am, but it doesn't know if I've ever spoken at this conference before? (I have.) Why are they asking me things they should already know?
And this is my message to you: Don't ask questions that will make your members or customers say "Wait, you should know that already!" Because every time you do that, you are telling them, "You're not important enough for me to bother working on getting this information. I'll just ask you for it because that's easier for me." (And as an aside, the customer may not know the answer, or may give an incorrect answer, in which case the data is useless anyway!)
I know how difficult it can be to integrate disparate systems or reference data from past events. But if that question is truly important to you, do the work beforehand or afterward. Don't make the customer do the work for you!