in general most cnc's will run at max rpm for years without issue . Where guys tend to run into problems is with putting faster spindle motors without changing the bearings on converted manual machines .
With that said , after dealing with 2 new fadals which blew their spindles within 6 months , we were told to drop to 80% because they weren't meant to run constantly at top rpm (which I called bs ). That was also 25-30+ yrs ago . I've worked on numerous brands of high and lower end mills and running at max rpm is not an issue