Ok, I’ll try again. After further review of Bosch’s Automotive Handbook, and no margarita’s this time…
By up-shifting at low rpm, you’re asking your motor to deliver power at its point of lowest “mechanical advantage”, which means you’re forcing the pistons, wrist pins, con-rods, crank, and journal bearings to accept the force of a large explosion pushing against a relatively unmovable object. Sketch out the kinematics and you’ll see what I mean. Yeah, I know the titanium con-rods have better fracture toughness characteristics than your standard NASCAR-issue steel con-rods, but the wrist pins and crank bearings are still susceptible to shear and just plain getting the crap skwarshed out of em. And the aluminum pistons are getting a hot fire on their face with no way to get away from it.
Continually running the motor at low rpm forces it to operate at less than desirable volumetric efficiency, which means that there’s not enough breeze flowing through the motor to blow out all that heat and combustion by-product adequately. Resultant to that is that the motor doesn’t achieve a good internal operating temperature, which allows the aforementioned gases to cool, and condense into gunk which will then apply itself to your plugs, pistons, et c.
Due to valve overlap, along with the stated low volumetric efficiency, some of those gunk-producing gases can emigrate out of the combustion chamber and blow back and settle onto the valve seats, or maybe even all the way around the valve, to collect on the stems and in the seals. That may not contribute directly to a loud valve tick, but it will likely eventually contribute to worn seals/seats. Then again, gunk buildup in the valve seat area would preclude full valve closure, effectively increasing the gap between cam & valve, making a louder tick.
Further downstream, your catalytic converter has to purify this flow, and, because the cat-con isn't hot enough, the same gunk-laden gases cool and condense in there, further reducing efficiency of the breezes flowing through your motor.
Herr Bosch points out, however, that a 4-stroke engine has “very good volumetric efficiency over the entire engine-speed range, low sensitivity to pressure losses in exhaust system, as well as relatively good control of the charging-efficiency curve through selection of appropriate valve timing and intake system designs.” What that means for us is that we probably don’t have to worry about gunked-up motors as much as in the old days, because Honda-san gave us some good electronics (and VTEC at the upper end of the rpm spectrum), to account for most of the undesirable low-efficiency effects. However, there’s still that nagging kinematics problem that can be cured only by changing lifestyle habits.
Give your motor a break. Shift at 4k, 5k…any additional induced wear is less of a concern than shearing wrist pins, burning pistons, fouling plugs, or squashing the guts out of your crank bearings. And you don’t have to spend a half-hour at high rev’s while you’re shifting. Make a moderately spirited acceleration, shift, have a little fun, listen to the motor sing, and then get into cruise mode. It’s a Honda!