12 years old might have a couple of years left and might not. Depends on their condition, teeth, udder, and how the lungs sound. As well as breed back.
things we look for
vaccinations what when
the bull used
HOw easy was the calving of the calves. Do they look like they are satisfied on the momma, or stealing milk from someone else.
how the bag looks. If the teats are nice breakfast sausage type or do they look like they could be icecream cones or waffle cones when they freshen...not the best. Is the bag nice and round like a soccer ball, basket ball, or does it look lop sided, or drag on the ground, front way up back way down.
Does it look like the teats and bag look like they are one in the same?
Body score
What type of feed are they on.
Heavy silage or corn can hide a multude of problems. They might not have the sane BCS on native pasture or hay.
Feet, long toes or nice and short. Walk nice or on the back hocks
How long is the tail...mother in law always said, long tail...good milk...dunno if that is true or not but got to keep MIL happy.
Just a few thoughts