As with all products, some fail before others. For large numbers of products the failure rate follows a Gaussian distribution. Whether they are made by Apple or one of the many PC manufactures, the Central Limit Theorem always applies because large numbers of board components are manufactured.
For every component that fails well before its mean-time-between-failure another component will not fail until well beyond the MTBF. Most components will fail. Two-thirds of all components will fail within one standard deviation of the MTBF.
No one likes to be have a failure in the skinny part of the Gaussian distribution – the 16% where the early failure rate within 2 to 3 standard deviation of the MTBF. But when a large number oc components are manufactured, this happens.
I have bought Apple computers since 1985. Not a single one has failed before the advancements in CPU/storage/memory/PS or applications made operation impractical. All this means is I was lucky and fell in between the one standard deviation failure rate.
Apple has three categories of for product support – normal, vintage and obsolete. Normal products are less than 5 years old and are handled by Apple retail stores. Vintage products are 5-7 years old. Parts and repairs are only available at Apple Service Providers in California. Obsolete products are older than 7 years. Apple provides no repair or technical support whatsoever. Here's a
link that explains these policies. Of course, non-Apple vendors can provide parts and repairs.
PCs offer more repair options. For instance, HP desktop PC support is typically lasts 10 years. The large number of diverse PC suppliers means replacement boards and parts are probably unlimited.
