When I worked for Douglas Aircraft in 1960s-1980s, the jet airliners were warranted for 60,000 hrs before any major structural problems would happen. That's eqivalent to flying 10 hrs/day, 6 days/week, every week for 20 yrs. Warranties might be higher today and even more on composite transports that don't have fatigue issues.
I mostly worked on R&D projects applying composite structures to the DC-10 and before we would place a new part on the plane, we sat in a conference room reviewing all the analysis and test data. The final question always was- "Would you put your wife and kids on a plane with this new structure?" If someone had valid reservations, the part would not fly until all doubts were answered. A great deal of consious thought went into design and verification of transport aircraft and we all took this personal responsibility very seriously.