Totally trivial I know! Not sure how it cropped up in conversation last night with a group of friends, but somehow we ended up talking about how long we keep birthday cards on display.
One person said they look at them and put them straight in recycling; one puts them up but takes them down the day after their birthday. The rest between 'a few days' and a week.
As said, appreciate it's really not important but am weirdly intrigued!