In know, beat to death, but I gotta ask.
The other day my wife bought a couple Romeo y Julieta for me. I went to light one up and it was like the whole thing was covered in sugar.
Now, is this what plume looks like?
If it is, then what is the difference that it makes?
I know, stupid question, but out of all the cigars I have smoked, these were the first I have seen the crystals and to be honest, they were not much different than the other RyJ cigars I have had.

Yep, that was plume. When you hold a cigar up to the light and see those little crystals winking at you, you know the cigar has been kept properly. Sometimes it can be very obvious to the eye. Some of the essential oils ooze out of the wrapper and crystalize. Does the PLUME do anything special? No. But it does mean you are smoking a nicely aged cigar. And if it is a good quality cigar, you will probably have a very satisfying smoke. I like to see plume. Mmmmmmmm,(drool) plume!

Though I have been thrilled to see plume appear on some of my older stored stock, I too wonder about its affect on the flavor profile, if any. My experience, so far, is it really dosen't make too much difference. The flavor of any smoke comes from the tobacco(s) it's rolled with. As the tobacco burns it releases the essential oils within the tobacco adding to the flavor complexity of the blend. If plume is the crystalized residue of the oils evaproating from the surface of the cigar wrapper, what have the evaporated natural oils (fluids) been replaced with in a well aged, well maintained cigar? Is it the moisture within the humidor? Either the distilled water or the pg solution? Are either of these really better than the oils lost? My experience with my older cigars is that it is a more mellow experience than the less aged smokes. Now my favorite flavor profiles lean more to the medium the medium/full flavor profiles. But occasionally a full flavor smoke is a real treat. Will these fuller flavored smokes loose any of their initial punch with age? Will a LGC Series R, or a La Aroma de Cuba (for example)loose anything with age? I know the Buc CM's that have developed plume in the 'dor seem to have the same flavor but maybe a little more mellow. If your one of those who really go for something with big spicey flavor, will you loose some of that edge with age?

To me, plume is a good indication that the cigar has been thoroughly aged and should be a really mellow smoke. One indicator is that plume does not develop quickly so there has been a significant amount of aging since the cigar was new to the point plume has developed. Having said that..........

I also believe that every cigar reaches its "peak" at some point. It may be several years but there is a point at which any cigar reaches its maximum flavor potential (as opposed to being simply smokable; I suppose a cigar can be smokable indefinitely if proper temp and RH is maintained). To follow on to what mrkmitch said, if enough essential oils in the cigar are leached out and crystalized, it would have to begin to deteriorate at some point, in terms of flavor characteristics.

However, to my knowledge, I have never let a cigar age "too long" and it's not likely I'll do so. The opposite is generally true for me; I tend to want to smoke them prior to their reaching that mellow stage.

Just my thoughts..............