It's a difficult question to answer, for me anyway.
If I buy 5 or so bottles, I will see which ones I really like and then order another 2. I sell it to myself with the following line "well, it might not be readily available in the near future"
Of course, it also helps knowing that good Whisky doesn't really lose it's value and is likely to only gain. So, in my mind, I'm not really spending money, I'm investing