Mario
As a protagonist, Mario demonstrates unwavering reliability. He appears whenever summoned, responds to controller inputs with pixel-perfect precision, and never once has complained about working conditions in the Mushroom Kingdom. His predictability is, in gaming terms, a feature rather than a bug.
However, closer examination reveals concerning inconsistencies. Mario's jumping ability varies wildly between games. His relationship with Princess Peach remains perpetually undefined. He seems unable to implement any lasting security measures against Bowser's serial kidnapping. The rescue-kidnap-rescue cycle suggests either profound incompetence or a pathological need for heroic validation.
Furthermore, Mario requires external power sources (power-ups, coins, lives) to function effectively. Without these supports, he can be defeated by a single collision with a slow-moving mushroom creature. His reliability, whilst impressive, is conditional upon environmental factors.
Time
Time has been ticking along with absolute consistency since the Big Bang. It has never called in sick, never taken a holiday, never once been late for anything (being, of course, the very standard against which lateness is measured). This is reliability of cosmic proportions.
The second is now defined by the oscillations of caesium atoms: precisely 9,192,631,770 vibrations constitute one second. This definition reflects our confidence in Time's constancy. Atomic clocks worldwide tick in synchrony, a testament to Time's dependability.
Critics might argue that Time's reliability becomes problematic when you'd prefer it to stop. The relentless march toward entropy, aging, and eventual heat death of the universe proceeds regardless of human preferences. Time is reliable in the manner of an unstoppable glacier: admirably consistent, ultimately crushing.