All my life I have been told that most engine wear happens at start up. I don't believe that. Every engine part still has a light film of oil on the surface from the last time it was operating. The oil pump puts everything under pressure very quickly at a time when the engine is under no load and the clearance between parts is greatest. Starting a cold engine on a highway ramp and hitting 65 mph immediately would be a bad move, but other than that all is well. Flow is a response to pumping pressure. It is not a passive movement. I believe most engine wear is due to time run, heat, and load. At this time, I must acknowledge that I could be 100% wrong.  

Define "flat".

This "belief" has likely been passed down the generations.....I don't know that any recent testing confirms that it is still true - or why the wear occurs.  Is it a lack of oil pressure, the poor clearances in a cold engine, or the unburned fuel/moisture causing issues?

Back in the old days before fuel injection, most engines were worn out at 100,000 miles.  It was common to see cars and trucks on the road with blue smoke coming out the tailpipe.  It was rare to see a motorcycle with high engine mileage that hadn't had a rebuild or two.  Rings would wear and get too big of end gaps, cylinders would wear and get ridges at the top, valve guides would get worn....sometimes the rod bearings would wear out on the top or bottom and you would get a rod knock.

Something has changed drastically, as even economy cars can reach 200,000 miles or more and still run fine (if the body holds up).  My wife's last 3 cars had more than 250,000 miles on them when they were replaced - they still ran fine but she travels alone a lot and didn't want car more than 10 years old and she replaced them.  My Pontiac Vibe has 160,000 miles and still runs like new, a fellow at work has more than 300,000 miles on his little Toyota...and another lady I know has more than 350,000 miles on her Toyota 4Runner.  There is a Honda ST1100 in the UK that got more than 350,000 miles on the engine, and it is not uncommon for the large touring bikes to get 100,000 miles without any engine work being done.....and Youzguyz got 160,000 miles out of a Savage engine using Valvoline and Rotella.

I think fuel injection is a big part of this extended life.  Back when engines had manual or automatic chokes - the fuel mixture was likely too rich for too long after the start up, and the extra fuel likely contributed to the piston ring and cylinder wear....maybe to the valve guide wear as well.  Fuel injection limits the fuel right from the first start and never allows there to be "too much" fuel.....so the oil stays where it needs to be and is not washed away by the excess fuel.

I also believe engine design has improved and materials have gotten better.

And finally....I believe modern oils are far better than was available 40 years ago - even the dino oils.  If we use a "top shelf" oil in our vehicles, use a viscosity rating that the manufacturer specifies, and change the oil and filter regularly - it is very likely that none of us will ever wear out a healthy engine.  In the Savage we need to use an oil with a good amount of ZDDP, we need to keep the idle speed up to provide oil flow, and we need to avoid idling the bike on the sidestand.

So if "most" of the engine wear occurs at "start up".....I believe the amount of wear is pretty minimal based on the life span of current engines and we really don't need to worry about it (there is nothing you can do about it anyhow).

"70% of all statistics are made up on the spot by 64% of people that produce false statistics 54% of the time they produce them".

Based on my observations it is definitely flat, however, I have it on good authority that it is a sphere

Take your pick

If the Earth were flat, say for example it was a cube, which is not possible because the corners could not support the weight of the rock and it would crush into a sphere. So lets say that it's a cube made of a material that will not compress.

OK so you have this huge flat plain, but what would it be like to walk to the edge, could you fall off? No, it would not be possible to walk to the edge any more that you could walk up the outside of a building.

Hotrod , you are wron... wron   ,mistaken!  flow is a response to pressure that's true. but they are inversely proportional , if pressure did it for your motor we'd all be running 90 weight oil. The flow of oil thru your motor is what lubricates it ,and carries away heat (really important in an air cooled motor) you need only enough pressure to circulate the oil,( about 10 psi per 1000 rpm) no more no less . Heavier oils will have more pressure , because of their resistance to flow. their flow being less puts a thinner layer of oil between the moving parts and bearings , and less flow carries away less heat. that is why 20w50  will make your bike run hotter than the 10w 40 on a warm day.
      Oil stays on all the moving parts ? that maybe true ,but only to a point , don't tell that to LANCER who fired up his bike with the high compression piston one spring and had to rebuild the top end. given enough time the oil will drain off. (zddp may help)
       I earlier stated that 80 percent of wear occurs at startup that was false , it's 90 percent . My statement that NO oil protects the motor at startup is true, the viscosity(thickness)of oil at 75 degrees can be 25 times it's viscosity at operating temperature ,and reving the motor at startup is bad because it increases the pressure and that decreases the flow when it's needed most . If most of the wear on my bike was riding it I be afraid to .
       On second thought your wromg

Well , I learned ... I need to use 10-40 NOT 20-50 in hot weather ?    

but

I'm still adding 1/2 can of STP and a little ZDDP to a 1/2 gallon of T-6 .

When my clutch started slipping (40,000 miles - ish) I thought the fiber plates were worn ... So I got a new set of fiber plates and new springs to go with them.  

It didn't solve the problem...

Further investigation showed that the aluminum back plate in the clutch pack had wore so much that no matter how much the springs pushed the guts of the basket together --- there wasn't enough stuffing inside the basket to be pinched.   The fiber plates are about .120" and the metal plates are about .060" .

So , I added another metal plate to the backside of the clutch pack.   now its as good or better than a brand new bike .   And yes I still use STP all the time.

Be advised : the push rod length might need adjusting to a longer length because the pack is now thicker.     Mine was still with-in the adjustment  length but yours may vary ???