Cats usually live longer than most dogs and it is no longer unusual for them to live until 20 yrs old or beyond.  A cat's lifespan is dependent on many things, including: Appropriate Consistent Veterinary Care, Diet, Genetics, and weather the cat is Indoor, Outdoor, or a combination of both. 

The rule of thumb is that at about age 7, a cat is considered to be middle-aged or a Senior. At age 10 and above, a cat is considered to be in old age.
Many cats at that age they do not look "older" and still have plenty of energy, however, underlying factor my be affecting their health.  This is why we stress the proactive approach to their health.   
   

CAT'S AGE               HUMAN AGE EQUIVALENT   

     6 months.............................................................................10 years

      8 months ............................................................................13 years
     
      1 year  ................................................................................15 years

     18 months ...........................................................................20 years

      2 years  ..............................................................................24 years

      4 years ...............................................................................32 years

      6 years ...............................................................................40 years

      7 years ...............................................................................44 years

      8 years ...............................................................................48 years

      10 years .............................................................................56 years

      14 years .............................................................................72 years    

      16 years .............................................................................80 years

      18 years .............................................................................88 years

      20 years .............................................................................96 years

As you can see a seven year old cat is well into their 'forties'. And since one year for a cat is equivalent to four human years, many changes can take place in a fairly short period of time. One of the reasons why the American Veterinary Medical Association as well as the American Animal Hospital Association now recommends semi annual physical exams plus appropriate blood work on all cats who are 7 years old or above.

Capital Cat Clinic recommends a physical exam every 6 months. Sometime this exam can include a work-up of comprehensive tests that include
    

*Blood Pressure
*Urine Analysis
*Thyroid Function Test
*Fecal Exam for Parasites
*Complete Blood Count
*Blood Profile

With these tests many health problems which are not readily detected and can be caught early on. Taking a more proactive approach is the allows for appropriate steps to be taken to ensure continued well-being and a longer life for your cat.