My Simi Valley tile roof is 28 years old and has never leaked. Am I fine?

You are fortunate and unverified, which are different things. The tile itself is likely sound for decades more; the felt underlayment beneath it was a twenty to thirty year material, and at 28 years it is at or past its design life across whole neighborhoods of this city at once. Roofs in that state commonly announce themselves in their first wind driven rain, at a valley or a headwall where the felt thinned first. The verification is cheap and specific: a roofer lifts a small section at a suspect detail, photographs the felt, and reports its condition slope by slope. Sound felt buys you a report to file. Brittle felt buys you a relay planned in a dry season at planned prices, instead of a leak's education in a storm.