When I use the New Posts link, the number of pages is always the same, at 40 This then includes old posts which I may already have read in the previous 24 hours, or even longer Is there a setting I can apply so that it resets based on the last visit?
It's not based on your visit date, it's based on if you read them or not. If you want to clear the list, use the "Mark Forums Read" option.