You should recommend Bitwarden Premium when specific conditions are reached like:
Number of Passwords is greater than 50 (or 100, 150, etc.)
User logged into the Bitwarden vault 100 (200, 300, etc) times
User logged into websites using Bitwarden 500 (1000, etc) times
User created 50 folders
…
This recommendations should be shown per condition only once.
So you show the message for 50 passwords only once, the next message after 100 passwords.
My intention is that this message is not nagging too much but reminds users from time to time to switch to Premium.
Something that came into my mind after the posting:
It is easy when you show the “Please consider buying Bitwarden Premium” message after the user has triggered some actions.
So read the list above as actions that the user has performed:
Number of Passwords is greater than 50 (or 100, 150, etc.)
Means after the user has added a new password and the total number of passwords is 50, 100, 150, etc.
This way the message is automatically shown only once (and when the user deletes password number 50 and adds a new one)
This way you have to understand the other entries in the list (add the text “After the user has…”):
User logged into the Bitwarden vault 100 (200, 300, etc) times
User logged into websites using Bitwarden 500 (1000, etc) times