I discovered recently that I like Macallan 12 better than Macallan 18. For me at least, there is such a thing as too much time in the casks. I had always heard that unlike wine, whiskey does not really change after it is bottled (reference, anyone?). The appeal of the age would then just be that there was a qualitative difference in the process or ingredients way back when? Without extensive taste testing, I would tend to expect that any marginal improvement (if any) as bottled scotch gets really old is minimal. The crazy market prices can probably be attributed to status-seeking behavior on the part of the buyers.