At the top of the list when looking at one account, it will tell you the last day/time it was updated. I would suggest that when looking at All Accounts, it should show me the last time all accounts were updated (ie: the last time/date of a full refresh).
I would also want the same date/time to show if just looking at "Banking" accounts or the other sub-headers.
Here are a couple of screenshots illustrating my idea: