I think it should last longer than it does ...
Hey, the actual answer is ... it depends. What the condition of the cigar was at the time it was put in the baggie, whether it has cello on or off, and what conditions the bag is kept in are all factors that will influence it ...
If you're looking to keep a cello'ed cigar in a bag for a time because you don't have a proper humidor, wet part of a paper towel with distilled water, squeeze it so it isn't dripping and put it in the baggie with the cigar ... try not to let it touch the cigar ... then keep the bag in a 70deg dark spot and it should be just fine ...