I recently set up email accounts for DS and DD, and plan to email them periodically, sending letters or pictures, for them to be able to read/have in the future, possibly at 18?

I'm curious for others who do this, what sorts of things to do you write? How often? Any ideas to share?

So far I have emailed both of them their birth stories and some pictures from their first few months.
I emailed DD today photos from a shoot of her in my wedding dress, along with the story of how I found it.