450 Upgrades for Engine & Bike longevity

You're on the right path. Keep changing your oil and use a clean air filter every ride. I also make sure my airbox and are boot are spotless before my filter goes on.

Change your Piston, bottom end and bearings at a reasonable interval.

Replace the 'T' shaped radiator hose fitting under the gas tank with a 'Y' shaped fitting from a 2015 and up model. It's $12 on motosport.com. I have a 14 model and it spits out coolant at the drop of a hat. Another good idea that I'm doing is to get a radiator overflow tank from a rmx450z(mounts underneath the rmx skid plate).

Honestly I'd say every ride is a little OTT for changing oil. If you use good quality stuff you can easily get 3 hours out of it. I change my oil every 5 hours and it still looks good then.
I would recommend changing the oil filter at every oil change though, or using a steel filter and thoroughly cleaning it. Also make sure you remove and clean the lower strainer filter (by the gear shifter) at ever oil change. Remove the springs and thoroughly clean the magnet and strainer.

A good skid plate is a good addition, keeps the engine cases and frame well protected. Always best to remove it when you clean the bike though as they can trap dirt and hold water easily.

I wouldn't say heavier clutch springs are a necessity, I'm still using the stock clutch and think its pretty damn good since I removed the judder springs and fitted some custom spring seating washers.

Be sure to run the bike after every wash to dry out. Also keep an eye on the plug and plug cap, it can get pretty shitty down there after a while.

I've put over 40 hours on my RMZ now and its been perfect with no faults at all. Use good fuel, keep on top of your filters and oil, pay close attention to your hour meter and replace engine parts at sensible intervals and you will have the bike for a long time!

I agree changing the oil every ride is over the top. I check mine every ride and once it starts looking dirty I change it...usually between 5 - 10 hours. 450s for the most part are bullet proof, most mortals can't ride a 450 very hard so they tend to last a lot longer. Change your air filter, use non-ethanol gas, service your pivots (steering bearings & Linkage/Swingarm/Shock bearings) once per year and don't spray the pivots directly with a pressure washer and this bike should last you a good long time.

I would service chassis bearings about every 15 hrs too. Swingarm, linkage, steering stem. This will help keep every tight and moving smoothly as well has help keep bolts from freezing in place. Dab of blue loctite never hurt on big chassis bolts either. Keeps them in place, seals threads against water and corrosion and removable with hand tools.

Your list plus proper maintenance is what makes a bike last. The second you stop giving it attention is when you have problems. Bikes these days are solid.