I recently did a tasting vertical of Glenfarclas 12, 15, 17, 21 and 25 along with the 105 NAS. I have full bottles of the 12, 17 and 105 NAS and got a sample set of the others to see what I was missing. My feeling is that I was not missing much. It seems like GF peaks at around 17-18 years with their production offerings. I suspect that any really good older barrels are being sold as single cask offerings. I found the distallate throughout the range has a consistent sherry and oaky profile with it getting a little spicier up to 21 years and more oaky at 25 years. In a blind tasting I don't think the 25 would fare as well as the younger offerings. The GF 25 really could use a higher proof. The flavor seemed thin and watered down and I really could not pick out much difference from the 21-year-old. It felt a little bit tired honestly. The great thing is that it is one of the most inexpensive 25-year old whiskys you can find, however, the downside is that it is obvious why it is so inexpensive. I have never had the family casks, single bottlings which from what I have heard is where Glenfarclas really shines. This may be the best example that "age isn't everything." My advice is to stick to the 17 and 105 NAS for your Glenfarclas fix.