I have some mead in bottles, which have been stored in a reasonably cool, dark place for possibly as much as two years old. I had intended to leave it for about a year for bottle conditioning, but now I'm curious what's likely to have happened after a couple years. Is it still safe to drink, and if so, how tasty is it likely to be?
Mead generally ages very well and some of the best glasses I've had are from bottles that somebody forgot about. (The only reason I've never had a mead that's more than ten years old is that it's hard to resist drinking a bottle that's seven years old.) Even unfermented honey is good several years later, and many meads take several years to develop their full flavor profile. If you try a batch a year after bottling and it doesn't taste great, see if another year or two improves the outlook.
If your mead has ingredients besides honey (particularly fruit), the flavor may worsen after several years of aging. Storing bottles on their side, which keeps the cork wet and therefore a better filter from the outside air, can help avoid developing off flavors as a mead ages.