Answer: Longer lifespan…but not by much! 

The adult Mayfly, found in the lower half of the United States, lives only one or two nights, while the average life of a mailer, once it has been filled and labeled, only lasts about 3-5 days.

Given the fact that you want to make sure your products arrive at their destination intact, and in some sense of aesthetic acceptability, you should do a little research and find out what mailers make their way best through the courier environment in their short life-cycle.

This is the gauntlet of the shipping world, and if your product can survive there, it will survive anywhere. Better yet, why not find out who the couriers are using, and save yourself the homework?