How long does compost take if you NEVER turn it?

I've never been a fan of turning compost piles. It seems like interfering with the natural process. After all, it's the various life-forms in the pile that do the real work of decomposition. We humans have a tendency to get competitive about everything, even how fast our compost breaks down. And that's the real reason we've made composting so complicated—we assume faster is better.

I quit turning my piles a long time ago. I also started building them directly in my beds—I'm not a fan of hauling anything around unnecessarily. But when a bin gets full, even I get impatient. I'll let it sit over the winter, then I fork the newer layers on top into a new bin to get down to the black gold and start planting things in it.

It occurred to me that I could save myself even more with a little patience. When the bin is full, start a new one, but leave the stuff in the old bin until it fully decomposes. I started searching to find out how long that would take. It seems the idea never occurred to many composting enthusiasts, and fewer had tried it. I found estimates ranging from 1 year to 2 years to "several years".

Has anyone had the patience to fill a bin and wait until the whole thing had turned to humus? 

Some data points: I make my bins 4 feet high by the width of the bed (4 feet in the past, but lately I favor 3 foot beds). The "ideal" bin size is supposed to be somewhere between 3x3x3 and 5x5x5. I add kitchen scraps and shredded paper as they're generated throughout the year, plus a heaping helping of garden waste and autumn leaves at the end of the growing season. In Wisconsin winters, the pile freezes sometime in December, and stays mostly frozen until late March or early April. Still, the volume has decreased about 50% by May. Assuming I take 1 year to fill a bin, then let it stand, how long would it take to break down completely?

The length of time may depend somewhat on what you are putting in the pile.  For instance, I built a pile last fall.  Mostly shredded live oak leaves and grass.  I turned it every 2 weeks about four times.  Then I let it just sit until last weekend.  About 20% of the shredded live oak leaves were still recognizable.  Everything else was fully composted.  I believe that it would take about 2 years for the leaves to fully compost if you just let it sit.

Before I started SFG, my leaves, cut grass, pears, small garden stuff was set in a pile, just a pile nothing like a fence or other.
I would lay in together as the fall season passed, it would be all ready for screening the following July. I never turned it.

On a side  note turning compost to me is a pleasure, I especially enjoy the wonderful aromas coming from a working pile, also to see the steam arising on a cool (not frigid) day. It seems to give me the feeling that wood chips gives to Paul Gautschi.
I only wish I had more time to do it..