So...if it eventually all comes down to personal preference, why do we need science?
The science of it all is actually fairly simple. We enjoy tobacco for its organoleptic properties - the effects it has on our sensory organs. We choose and appreciate our cigars for their taste, aroma, mouthfeel, texture and appearance. The only sensory organ missing in this lineup is sound...and if your cigars are speaking to you, they may be rolled from something other than tobacco....
Since tobacco is an organic compound, it will, for all time, deteriorate until it returns to its original form of the molecules it was before it became tobacco. And since we know that NOTHING on Earth can live without water, we must ensure that our tobacco of choice has the amount of water it needs to sustain its useful life. That's where the past couple of decades of paying attention to such matters comes in handy. We have learned that cigars or pipe tobaccos that are too dry burn faster, smoke hotter and have flavor profiles that tend towards things that are burned, charred or otherwise spicy. We have learned that cigars or pipe tobaccos that are too moist burn slower, are hard to light and draw slower with less smoke production and sometimes unpleasant vapor production. Therein lies the 65-75% RH range that we as consumers have defined by our spending. And while some cigars and pipe tobaccos may be preferred slightly above or below this range, they are more often the result of individual tastes than that of most consumers.
Within this range lie most of our preferences. Some like it hot, some like it cool. Some like it sweet, some like it spicy. Some like it earthy, some like it smoky...the list of comparisons could go on and on. Almost without exception, it stands to reason that these preferences are considered highly when preparing tobacco blends. The 65-75% RH range has become established as such because it serves to preserve the flavor profiles for which each tobacco in a given blend were chosen - and to maintain that preservation for the longest time possible.
One last footnote on the 65-75% range that we consider is the geographic climate of the storage area. In hot and arid climates, we would need to default to a higher end of the range than we would in cooler and more humid areas. You might likely use a 75% RH Boveda pack in Phoenix to achieve the same result that a 65% RH Boveda pack would in Tampa. At the end of the day, most people land somewhere in the middle, or as you may have heard or seen before -- 70/70.
--Danny Jackson