determining adult mouse age

Question
How can I determine the age of my two mice there names Pinky and the Brain. I was wondering if I can determine the age of my mice by looking at them or something on there body, without having to take them to a vet, which I know will cost a lot of money. Any info would be great and thank you.
                                Fiona, I love my mice

Answer
Dear Fiona,

Someone who knows mice could tell if a mouse was pre-adult, or whether it had a younger, middle-aged, or elderly body, but mice age differently and one mouse can look elderly at 15 months and another still be hale and hearty at over 2 years.  Your vet may have very little idea of their age.

I'm trying to figure out why it could be important to know.  There is no reason to treat a mouse any differently depending on its age.  When I call a mouse elderly, I mean a weakened and changed body type that can occur at any time after about 15 months but sometimes not until twice that age, which often but not always suggests the mouse is near the end of its life.  Mice also don't care about age. In terms of dominance, they care about size, strength, and relationship.  

If you tell me why you would like to know maybe I can help you.  I certainly agree it isn't worth a vet visit.

squeaks n giggles,

Natasha