I almost never write in the same fandoms that I request — I think only in 2014 did I request (and receive) a fic in one fandom, and get assigned to write for that fandom too. I don't think I'll be writing in the three I've requested this year, either.

The app is so useful for getting an idea of the types of requests you're likely to match on — so helpful if you want to make a really careful choice in terms of offers!