Thank you!
Yeah, it's M&P. ::snicker:: more coffee?
When I first finish my bars, I let them dry on paper towels for about 12 hours, then wrap them in plastic wrap tightening a tiny bit with my heat gun. I let them sit for about 4 weeks, then unwrap the plastic and put them in their retail packaging. The plastic wrap will keep their moisture at the right level, while they do their slight evap/shrink process, and after that period they're not likely to shrink much more in their actual packaging. Unless I'm careless, and leave them where it's too hot or dry for too long at a time. I've had crumbly little glycerin bricks by accident, a few times lol.
As far as airtight, I know all the guides say yes, but unless it's a bar that is really intricate, or I'm worried that my bars will dry out more rapidly than they should for some reason, I don't typically see the need for it. I have bars over a year old that are still as moist with conditioning and lathering goodness as the ones from yesterday.
::edit::
I don't know if it makes a significant difference, but I thought I should mention that I live near Seattle, so it's somewhat humid all year long, and that helps to keep the moisture locked into M&P a bit more than a drier climate would. I've only had two dew issues, conversely, and that was because I had added too much additional oil to my batches in the beginning.
