DANGER: High Humidity!
"I use a humidity controlling liquid and distilled water. Will this excess humidity harm my cigars? I have always been under the impression that the 68% - 72% humidity range is ideal, and your cigars will age well and last indefinitely."
If you can relate to the above scenario, you've got a problem, or you're going to have one at some point. Assuming the average temperature in the humidor is around 70 degrees, your cigars are going to smoke more like a ShamWOW! than a cigar. If your humidity levels are running as high as 77% or higher, you risk mold and possibly hatching of tobacco beetle eggs.
One thing that contributes to high RH levels is oversaturation of your humidifier. You may be recharging the device too often, or you're using too much solution (a.k.a. polyglycol) and/or distilled water when it comes time to recharge your humidifier. My cigar humidors are now well-seasoned enough that most of the time I only need to add a little squirt of a 20% solution to 80% distilled water mix I made up. So if you're completely soaking the humidifier each time you recharge, you may be overdoing it.
In recent years, the 70/70 "ideal" standard has had some holes punched in it. Your cigars will fare much better at an average relative humidity of more like 67%. Even at that number, some cigars can be overly moist, but try not to stray too much farther down from the "norm" than 65%.
If your RH is running well over 70%, remove your humidifier/s from your humidor/s until the RH has had time to dip. Let the humidifiers dry out some, too. (You can even leave the lid up for several hours to help it along.) Note how long it takes to get the RH down to about 67%, and see how long it stays that at around that mark. Check a few of your cigars every day by giving them a little pinch to see how supple they are. Once the RH hits 64%, replace the humidifier/s and try to keep the RH at an average of about 66-67%.
Your cigars will age better and last longer at a cooler temperature and lower humidity, more like 65º/65 RH as opposed to 70º/70 RH.
ShamWOW!® is a registered trademark of Shamwow, Inc.