From the spring of 1998
Dr. Jennifer Coates at PetMD answers the question "How Long Do Cats Live?"
Another statistic that I commonly use in practice is that cats that spend significant unsupervised time outdoors tend to live to be about 7-years-old, while indoor-only cats can be expected to make it to around 14 years of age.
In her prime, Boxer spent 'significant unsupervised time outdoors'. In fact, she experienced her own 'incredible journey' when she was 7 or 8, disappearing for a week and returning home unscathed, waltzing into the house as if her absence was no big deal.
She's one hardy and very healthy cat.