I don't think it is a good idea and would furthermore not buy cigars if from a place that had this as a practice. We all know how a cigar taste if you re-light it after a too long rest.... If you smoke in a walk in amongst all the other boxes, there is bound to be smoke going into the boxes and would lay as a film on the cigars (not even thinking about going into the cigar as I think the risk for that is minimal).... This smoke would obviously go stale and eventually start effecting the cigar. I don't think that one or two cigars would make much of a difference in a walk in, but if it is a frequent practice it would.
The only way to stop this smoke from going stale is by having a really good ventilation system to extract the smoke, however, I don't think this is a good idea either as there is no ventilation system that won't effect the humidity.. and further, as I believe in reducing the amount of air reaching my cigars on a constant basis (for ageing purposes)... to not only allow the normal air circulation but effectively replace the air in the room in a rapid speed (the ony way the could get rid of the smoke) IMO will speed up the maturation and thus render the cigar unsuitable for long term ageing at least.
This is only for places that have their cigars in the open in the walk in.... I have seen places where they have cabinettes with glassdoors along the walls.. and you walk into a room and can see the cigars... this to me is not really what I class as a walk in humidor.. the cigar environment is then restricted to the cabinett and not where you are when you would be smoking so this would be a situation where the ventilation etc could be organized... but with a real walk in so you walk into the cigar environment when you enter... no.. no smoking there....
Sleeping in a walk-in however is heaven!!!! just my 2cents though...
