When is it ever time?

When is it ever time? When is quality of life so low that I must let my little girl slip peacefully into an eternal sleep, never to see the light of day again? When is it time to let that dog go?

The dog who is 13 years old and has had Cushing's Disease for over a year;
The dog who has been part of my family for over 12 years, more than half my life;
The dog who walked me to elementary school and was there at the street corner waiting to walk home with me when the bell rang at the end of the day;
The dog who ran around the yard with a toy soccer ball while 8-year-old me chased her;
The dog who I took running when I was in middle school;
The dog who could always play with visitors and friends and be trusted to behave nicely;
The dog who was a member of a secret club with my brother and me in the backyard one summer;
The dog who came to visit me at college my freshman year;
The dog who watched out the front window as we drove away and ran as fast as she could to the front door when we returned home;
The dog who was my very first passenger after I got my provisional license;
The dog who joined our family on a two-day road trip to my grandparents' house when she was 2 years old;
The dog who went to show-and-tell in 4th grade and again when I was a senior in high school;
The dog who has been the quintessential childhood dog...

Mali in the backyard, 2006

Who am I to play God and decide the date of her death? Then again, who am I to let her suffer until her natural death? At what point does senility become suffering?

If she still wags her tail when talked to, does that count as happy? Or does her spending most of her days lying around in the kitchen mean she's unhappy? Does the fact that she can still go for walks constitute quality of life, or does taking twice as long as it used to take to complete the route mean she's too sick? Does enjoying her meals make up for the unpleasantness of bumping into walls and objects because of her blindness and dementia? Is it fair to ask my parents to continue to care for her as her health declines? She's given us so much; what do we owe her: more time, or a comfortable exit?

Mali snoozing in her bed, 2013

This is absolutely the hardest decision a dog owner will ever make.