"Open when..." envelopes! These are perfect for military deployments or long distance relationships, etc. I grabbed 10 envelopes and put hand written letters in each of them, some with little treats. I also made an 11th envelope for just pictures!
Open when letters!
Open When Letters (great for anniversaries!) by TheDelicateDinosaur on Etsy https://www.etsy.com/listing/219300598/open-when-letters-great-for