Pretty much all mechanical parts have a finite lifespan. Electronic boards are not unique in that respect, and in fact their reliability potential is better than average since they have no moving parts. When's the last time you "changed the board" in your car? Electrolytic capacitor lifespan varies drastically based on specifications and operating conditions - they can last decades if properly specified.
Yes, there was a capacitor plague a while back that led to a higher than normal failure rate. As with the scare stories about self cleaning, that was an aberration, not representative of how that technology works normally. Electronic control boards have been used in the vast majority of American made ovens since the early/mid 90s - after that time only BOL models, many Euro import models, and some "commercial style" models were still using manual/mechanical thermostats. I see boards from the 90s/early 2000s all the time that have been working fine for decades.
That's not to say electronic boards are perfect. They have lots of sub-parts and can be complex to design, which creates the potential for introducing problems, and certainly some board designs have had their share of issues. They are relatively expensive to replace and their sub components are generally not designed to be serviced (at least in the appliance industry) so are a contributor to driving up repair prices and junking appliances young. But to say electronic components inherently have shorter lives than mechanical components suggests a profound ignorance of basic engineering.
