Depends on the owner who takes care of engine and the manufacturer who makes the engine.
Let's take Hero and Honda.
Both produce the same 150 cc engine for Xtreme and Trigger respectively.
Which lasts long? Hero lasts longer, because of the quality of materials they use in their parts and their ASS
' mechanics are good (except few).
Why Honda doesnt last longer, Honda has gained the brand image and started cheating everyone by manufacturing parts that are inferior in quality even inferior than Bajaj and TVS (not mentioning that Bajaj and TVS are inferior, they are also doing good, doing better than Honda).
Now let's take two Pulsar 150s (both DTS-i).
Give it to two person, one is a rash driver and one is a sedate driver.
So clutch plates have worn out in both bikes.
The rash driver's pulsar's clutch plates worn out in 25k kms and the sedate's one lasted for 40k kms.
Why much difference, it depends on how they take care and ride their motorcycle.
People should not blame the manufacturers for inferior products offered by them.
No manufacturer wants their products to be inferior, if they wanted to be like that, then why and what's the point to invest such a huge money on developing that concept and making it to the production line?
So, again, it all depends on the owner and a part of it depends on the manufacturer and its service centres.