If you want to stabilize the cigar for better burning characterists, usually 2-4 weeks is sufficient depending on what condition you got the cigar in. You want the moisture content to become even throughout the cigar. It takes longer for the core of the cigar to dry or pick up moisture. After a while you will recognize the right "feel" and "sound" of the cigar when it is gently squeezed.

If you want to age for taste, most cigars do get better with age, but some don't age well, even afte a few months, and ought to be smoked as soon as they are smokable, In my experience, the Partagas Black Label is one of these cigars. I have also heard some say that the Padron Anniversary loses something after a year or so.