It's a gamble! We're facing this issue in our planning, too. My FP+ are generally in the late afternoon or evening (between 4pm and 8pm), and we've decided to keep them as they are. First off, we take a big afternoon break from about 1-4, and have our morning structured to take advantage of rope drop and then move into "anytime attractions" after 10am, so we really don't need FP+ any earlier in the day. Our plan is, if we use all 3 and can get a 4th, great, but we're not going to depend on that for any headliners. (Plus, my personal suspicion is that the only FP+ that will be offered as a 4th or 5th, etc. choice will be those that are already left in the FP+ inventory for that day -- the "leftovers," if you will. That means that the super-headliners may already be gone partway through the day, anyway. But that's just my theory.)
Not only that, but there is a certain symmetry to hitting headliners at rope drop, going at a more relaxed pace for much of the day, and then finishing off the evening with another set of headliners (this time with FP+). It gives us a nice "arc of excitement" throughout the day. 
