I've owned many motorcycles: from old classics to scooters, superbikes, unknown Chinese brands and even a few custom built ones.

Motorcycles are very reliable, as long as you know how to perform basic maintenance on it, or take it to a reputable service centre if you can't do it yourself.

The most important aspect would be to make sure that the oil is changed frequently (usually around 3000km - 6000km depending on the displacement) along with the oil filter, and if it is liquid cooled you should always check the coolant level before riding and top up if needed.

Now of course, as with everything else, if you buy a motorcycle of low quality, it might not be as reliable. So try to spend the little extra to get a well trusted brand such as Honda, Suzuki, or Yamaha (to name a few). But even a motorcycle of high quality can be driven in a way that will surely shorten its lifespan, like pushing the revolutions beyond the recommended limit (red line). The displacement size (CC) will also play a role in how many kilometres you might expect to get out of it. Usually lower displacement engines have a lower expected lifespan and vice versa.

At this moment I drive a Honda CB300F. In 2 years I've put 42 000 km on the clock. I don't plan to sell this one as it's a great daily commuter, and I'm certain I can get 150 000 km out of it, or even more.