DIY Invitation Question

I bought all of the cardstock and envelopes for my DIY invitations. We sent the card stock to the printers (we designed the images and are having it letterpressed) and should get the completed product back in about 3 weeks. We don't plan on sending the invitations out until the beginning of June, so what is the best way to store them?

We are also getting calligraphy done on the envelope. How long should we wait to get the calligraphy done so it doesn't run, bleed, fade, etc...

TIA!!