How do you get high mileage from bikes?

Observe the service intervals:

Change the oil on time. Use high quality synthetic oil. Group IV where possible.

Ensure the valve's are kept within their specified clearences.

Refresh the cam chain/tensioner every 30k

Use OEM filters not 'high flow super amazing' ones from K&N.

Show some mechanical sympathy:

Warm the bike for 5 mins before moving off.

Change gears properly etc.

Keep it dry and/or covered.

Most people don't realize it, but the engine is the last bit to wear out on a modern motorcycle. Everything else will fall apart long before it does!