It very much depends on when you are there. We were there in early November and, not thinking about it, didn't schedule our original 3 FP+ to be completed until pretty much 3pm every day. With shorter park hours, and parties closing the parks early, there was very little in the way of a 4th FP+ by that time of day. We tried twice, found little, and didn't bother the rest of the trip. If we were going again during party season, we would aim to have our original FP+ done by 1pm at the latest.