The highlighted term "longer", I think it should have been lower.
What is longer reliability?
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If probability of successful operation is the opposite of mean time to failure MTTF and failure rates are constant for each part, then longer MTTF’s result in longer reliability periods. But confidence factors are used here for the probability of MTBF and FIT rates.
Preventive maintenance test plans also increase the duration of reliability. These intervals are adjusted according to the margin of the test results. In the grid power industry, they often have 4 levels of ratings for each test type from annual, to monthly to weekly to remove and replace for escalation levels of monitoring margins. E.g. explosive gas concentration levels, temperature rise, PD levels, etc.