cheezz, it lasts for months--both unopened and opened. I make batches (about 6 jars) and
keep them in the frig until I mail out as "thank you's".
Lately, I've been using the "flat rate envelope" to ship. This brings the mailing cost down to ~$6; I'm pretty darn sure the USPS never expected a flat envelope to bulge 4"! But hey...it seals and the USPS commercial brags: "If it fits, it ships." I'm just taking them up on their offer.
I'd still like to try vacuum-sealing it in 2-oz flat packages (like Justin's Peanut Butter packages). That would be easier to mail out.