It depends on a variety of factors:
-How long was it at the vendor?
-Does the vendor keep them at smokable rH, or at a higher rH to help protect the cigars during shipment?
-How far away is the vendor, and what was the travel time?
-What were the conditions like during that travel?
-Is the weather hot or cold, humid or dry where they were shipped from/to?
-How were they packaged?
All of that can play a factor in how the cigars arrive to you. My rule of thumb is at least a week of rest per day the cigar was in transit. No scientific reason, and probably overkill. If it came from one of the big boys and is a massive production cigar likely to have been in their warehouse for a while, I let it rest a good couple months at a minimum for the rH to acclimate down from the warehouse rH (likely 70%+) to where I like to smoke (62%-65%).
Additionally, many cigars perform a lot better after 6 months of resting, gets rid of the initial sick period/ammonia buildup/whatever, so for many cigars, I don't even bother with them for at least that long regardless of where they came from. Things like AJ Fernandez blends, Ramon Buesos, the 601 blues back when I used to buy those, etc.