I have always been told, and therefore I have always taught that honey lasts forever. That it is just as sweet and viable after 1000 years as it is today.
Obviously, it was totally crystallized. I have a warming blanket that wraps around a 5 gallon bucket and heats at a perfect temperature of 115 degrees. After about 24 hours, it was perfectly de-crystalized. Very dark honey, it looked like knot-weed honey for sure.
I transferred it to another 5 gallon bucket that has a spout on the bottom of it so I could drain it into bottles, etc. But, it's the worst tasting junk I have ever tasted in my life. It's down right nasty. I put the old bucket out for the bees to clean up. They won't touch it.
In my research, I have learned that honey stored in a heated environment will go bad, very bad. Turns out that my friends have stored this honey in their garage next to their water heater for about 10 years. At times, in the summer it gets 80 to 90 degrees in that environment.
The condition is called Hydroxymethylfurfura (HMF). HMF occurs naturally and all honey has minor bits of HMF, but with overheating for long periods of time HMF develops exponentially and ruins the honey. It is toxic to bees and that's why my bees won't touch it. I read that HMF can have serious effects on your health. It can permanently damage cells and DNA.
Honey therefore will last forever IF it is stored properly in a cool environment.