There are two pieces to the question, I think.

One relates to humidity. I believe many online vendors keep their cigars a little more wet than I want (and a few shops, I guess). I've had way too many that just wouldn't burn right, and I had to light and relight over and over. My personal thought is that 8-12 weeks of rest seems to be enough to get cigars from wet to smokeable at my preferred humidity (65%). The trick is that I'm sure some cigars arrive at the house perfectly acclimated at 65-68%, but I've got enough stock now that I don't mind just letting everything sit for a while. So on this part, sometimes a cigar is perfect ROTT, other times it may take a few weeks or more to come down. I've heard of guys putting the cigars and a hydrometer in a ziplock or tupperware with the cigars for a couple hours, but I have no idea how accurate this would be.

The really tricky question to me is on particular cigars, and which benefit from a longer rest/aging. I've smoked a bunch lately in the 1-3 year old range, and very few of them have gotten worse in that time, but frankly I don't think most of them have gotten a ton better either.

A few do seem to benefit some though, especially my beloved Oliva Vs. A bunch of people talk about aging Fuente Anejos, and after a couple years I actually can tell a difference with them - I love them both, but not sure if I prefer the punchiness of the newer ones or the smoothed out older ones.

I'd basically think of under a year or 2 as resting, and more than that aging...I guess.