One thing we need to get straight is what is meant by "cruising speed" as opposed to peak MPH.
It appears that some of you are using "cruising" to mean where a guy peaks on a typical day as opposed to his best day.
Others are using "cruising" to mean where a pitcher throws most of his fastballs. That is, he has the capability to throw harder, but he chooses to stay free & easy most of the time in order to have a little extra "pop" to surprise a batter with when needed.
PG, you mention some names and I will point to Melville as an excellent example. I have seen him out there throwing 87-88 without the least bit of strain. Then maybe he gets a guy in scoring position with less than two outs and needs a K, so suddenly he's pumping 92-93. This is just a talented guy who's showing he's also smart. If he'd been throwing 92-93 all day, the batters might have him timed. But 87-88 is hot enough to put most batters on the defensive, while still leaving him room to "reach back for something extra".
I would argue that for a pitcher who has the physical capabilities and the smarts to do this, 92-93 is the relevant number to discuss, not 87-88.
That's not to say he may not have a day where he doesn't have his best stuff and might not peak at 87-88. But if you're evaluating what a pitcher has to go to, it makes no more sense to judge him by his "cruising" velocity than it does to evaluate him by the MPH on his curve or change-up. Peak velocity is the relevant number for evaluation purposes.