As long as you buy your miter saw from a reputable company, there is no reason why it would end up breaking down all that quickly. In spite of the fact that this is the case, nothing lasts forever. Hence, while you can rest assured that your miter saw is going to last a very long time indeed, you should still be on the lookout for signs that it needs to be replaced at the end of the day.
It is important to note that the biggest sign that your best miter saw should be replaced with a new one is if it starts to get a dull edge. If the sawing motion takes a lot more effort than it used to, this means that the miter saw is past its prime and trying to use it further would only damage it beyond repair. You don’t necessarily have to buy a whole new machine. Instead, you can just look at replacing the saw bit as this is the only part of it that needs to be changed and the rest of it probably works just as well as it always did.
You can save a lot of money by replacing the part that needs to be changed rather than just buying a whole new product. Miter saws are expensive after all, and replacing one on a more or less regular basis is just not a very financially viable way to go about living your life. The best way to save money with a miter saw is to take it to a professional who will tell you what can be done, and chances are that this professional would be able to repair it.