I am doing that, but I want to know the exact minimum usable retention.
The Compute button used to suggest 83% for most decks when I specified all cards and 1-3 years.
I set 83% for the least important decks, increasing by 1% per priority level (except for the top priority ones with 93-96%)
But then I tried this:
“amount of new cards per day × days in 3, 5, 10 years + amount of reviews due in the next 3, 5, 10 years”, time/day last year.
and Anki suggested 84-87% for most decks, although 80% for one. It wasn’t proportional to whether I review the decks on time. The 5 year suggestion was usually lower than the 3- and 10-year ones.