I did try an avocado honey mead one time. It was tasty. Gave almost a bitter/fatty tinge to the aftertaste, like an aftertaste of an avocado. While a very mild aftertaste, it was delicious, and quite unexpected in a sack style mead. And I did ask him if he added an avocado to it, and he swore the flavor just came from the honey. It was very recognizable.
The gentleman who made it, however, said it took a long time to smooth out - and he was an experienced mead maker. I believe he was talking in the 3 year range before it became even remotely drinkable.
Being in Arizona, with all of the citrus trees around, it is very common to have orange blossom honey, and I've never heard a similar complaint about orange blossom honey. Orange blossom honey seems, to me, to be a more typical aging time. (I consider this ~1 year before it starts tasting somewhat good ... wait longer for better results, etc)
It may have just been the honey he got, or something to do with his process, but that is my experience. Your mileage may vary.