Optimum Frequency for Cream Application?

I met a 60year old woman that I took for an older sister of her daughter because of her lovely skin. She told me her secret was to apply inexpensive cream (Yves Rocher) three times a day instead of twice a day.

What would be the optimum frequency for skin cream application? For how long do the different active cream ingredients (e.g. retinoids, AHAs) stay active in contact with air and have a chance to penetrate beyond skin surface? And what would be the best frequency to reapply a sun screen?

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