Charlie, I've got a lot of used planes that haven't been remouthed. I wouldn't normally buy them (the planes) in that volume, but I figured if I bought them right and I was going to try to make my own planes, one of the dumbest things I could do is go cheap on the subject tools and end up making a plane that wasn't better than what I could buy. I've been down that road in the past, too.
Of all of the planes I bought, one was remouthed, two were opened (very sloppily, almost as if they were done with a rasp and then filed smooth), but most were left alone. One of the things larry talks about is slowly conditioning the soles to keep the mouth in order. On a double iron plane, you don't have to work the sole unless there is twist in the plane that occurs over time, so all but the most abused of double iron planes I've bought and seen have been with original mouth - some of them so lazily made that they abutments were cut all the way through to the mouth (later ones), which creates a very ugly plane.
Anyway, I doubt that we work that differently. If I have a board that has twist, I remove the high corners first (not by planing the entire board, but just by removing the high spots). I hope that by the time I've jacked the corners away (or used the try plane if the board doesn't need a jack plane), that I've got a board that's already flat and clean and that the try plane and then smoother don't have to do much. I would be surprised if that was more than 1/8th inch on many boards. Hidden in there is the ability to use the try plane to take quite a lot at a time without tearing out. I try to work after the jack at 80% of what I could do, which is often shavings of 7 or 8 thousandths (in stuff like cherry, a couple less than that if maple/beech/ash), and not that many until a board if flat to the bench top.
The point is that all of this is easier if there is *no* or nearly no tearout. Whatever small amount the try plane might leave is literally removed in one or two heavy smoother shavings, never more, or you threaten flatness or if working to a mark, thickness.
It just isn't quite as fast with a small aperture because you have to work a thinner shaving and you're dealing with a little bit more tearout until the final stroke.
I don't leave the mouths on any of my planes really wide open, but when I make one - especially a jack, if I can feel resistance after I make it, I will open the mouth until I don't. It does provide some protection at the jack step, but not really routine tearout protection, more disaster avoidance.
if I had to pull a number off of the top of my head, I'd say the cap iron doesn't really reduce anything at the jack step, that's more a matter of reading the board, but over the process if the wood is anything less than perfect, it's probably a labor saver of 20-30%. You can smooth with a good surface until clearance of the iron is gone, same with the try plane - it will stay in the cut much longer (more volume of wood removed) than a similar plane type of single iron. It's true the single iron is a little faster to resharpen, but when that happens twice as often because the plane doesn't stay in the cut, it's a net loss.
I provided a couple of planes to brian holcombe and suggested all of this stuff. I'll see what he says, he's working entirely by hand. He already made the remark to me several times that with the try plane set, he can tell that it's getting dull but still get it to begin a cut cleanly and stay in the cut and leave a surface that doesn't have nick lines in it. These kinds of subtleties are a pain to discuss on the forum, because everything becomes a straw man. I'd be able to prove what I say in person pretty easily, but to address something that derek asks, what exactly am I trying to sell? Nothing, so i'm certainly not going to put together a huckster wagon to go prove a point. Anyone ever in my area is welcome to stop by.