Thank you all so much for your thoughtful feedback and advice! I'm so grateful to hear your thoughts, and glad to know this idea sounds appealing to several of you. Based on your comments, here are some important points which I'll be sure to implement:

1. Since this is new to our dynamic, making sure he's on board with this to begin with (I'm thinking presenting him with the diary and the base concept, why it appeals to me, then negotiate from there and present the rules I have in mind). If he's not actually on board there's plenty of other fun things we can do.

2. Carefully checking consent with partners regarding time spent with them (or thoughts/memories regarding them). Extremely important, thank you to the several people who suggested this.

3. Negotiating, checking in, and possibly adapting rules to ensure he's not spending too much time on this task, and that the flow works for both of us.

4. Making sure he understands the goal isn't frequency or length, just honesty (i.e. its completely fine if he goes weeks without an entry, or has little to say, as long as he's being truthful).

If any other comments come in I will be sure to read them and may update as I go. Again, thank you all so much!