The majority of bottles won't appreciate in value. Perhaps maybe the Chritophel and Baccarats only.
Do u purchase mainly empty bottles, or does it matter?
Do u buy because you love the bottle, or with an eye toward price appreciation and re-sale value?
For me, I collect art as well as bottles. I regard them in the same light as works of art. If I am able to get a good low price, so much the better. Sometimes I do pay current market value for something really special.
See my blog; http://www.basenotes.net/blogs/2645-kumquat