Not sure I fully understand the question. When you say you’re referring to your first three FP+, what do you mean? Do you mean use them right away? Use them at all? Not quite sure.
Generally speaking, we use our first three FP+ ASAP, we see no reason to “save” them. As for how often we use them in general vs. just doing standby…if the ride has a FP+ queue, we almost always use it. Sure, if it’s mid-summer and we want to ride Nemo in Epcot, we may just do standby as it literally has no line. Same for Pixar short films. But anything that has any kind of line, even 10 minutes, we use FP+.