I narrowly avoided deleting months of someone's work once - it was in a directory called 'temp', and I assumed that emptying it was a good way to free a few gigabytes of space on a full disk.

My inbox has 138 items, all read. If there's something that needs dealing with later I move it to a folder called "to do", and anything older than a week gets shifted to an archive (which goes back about ten years). I regularly see colleagues with hundreds of unread emails - one (thankfully now departed) used to let them pile up for weeks and then deal with them all at once, so I'd get replies to half a dozen urgent enquiries on a Sunday afternoon six weeks after I had found out the information by ringing her secretary.