[kruuth]

Is there a way to log what videos are being watched on a kodi instance? I want to delete some of the older videos nobody is watching.

[BigNoid]

You can make smart playlists based on "last played" and "playcount".

[PatK]

I'll agree a smart playlist would be what you're after, but this shameless plug for an add-on might have some purpose http://forum.kodi.tv/showthread.php?tid=279131

[nickr]

I tend to get the family around the table (after dinner is a good time). Ask if anyone wants to watch X again. Delete or keep accordingly.

[Atreyu]

There is a nice addon called Last Played that shows an arbitrary number of last watched items from anywhere.
I use it to quickly return to what has been watched.
You can have time and date added so that would give you a list of watched items by date

\ edit just clicked PatK's link, so just consider the above a summary ;-)

[kruuth]

Play count? How do I use that?

[PatK]

You would specify the playcount number, lets say 2, then every video that has been played twice would show up, delete from that point.