How long can a iPad Pro last

iPad (or indeed any electronic) device does not have a definitive lifespan. Whilst the product will have reasonable expectation of update and repair support from the manufacturer for a number of years, an electronic device can suffer an unexpected failure at any time.

Whilst early failure is unusual, it not impossible. All devices have an expected lifespan - often quoted as MTBF (Mean Time Between Failures). This is a statistical measurement that represents the statistical “mean” (i.e., average) period of time that a device will operate without one of its hundreds (or more) of its many individual components suffering a fault. Being a statistical measurement, an “average” is just that; some devices may last longer, others may fail sooner. The actual MTBF figures are not published by Apple, but perhaps suffice to say that the device warranty is intended to “capture” and remediate early failures.

Failures can occur for many reasons - and not all failures (e.g., mechanical shock) will necessarily leave visible or cosmetic evidence of damage having occurred.

You may just be unlucky - and have a device that, for reasons that will never be known, has developed a fault somewhat earlier than you might hope - but beyond the period of your device warranty. Your older iPad may be equally lucky in having lasted as long as it has without issues - although I might suggest that your older iPad is operating closer to the lifetime that I have experienced for most (but not all) of my Apple devices.

Taken together, your old and new iPad might be closer to the anticipated average usable lifespan.