I assume he has a VJ because it sounds like it
I ALWAYS change mine out when the alarm sounds. I know there is some ink still in there but I have had bad luck when it runs out completely (you can see where that color started fading. And like I said when it completely runs out the print head just sits there so if it is left it dries out. And the alarm is annoying, you can cancel it but then when it runs out completely and forget you get trouble. If it sits there for a hour you have to soak for 4 hours at least to get it back. Maybe this procedure is wrong but it is how I have been doing it for over 4 years with little problems.
You have to be careful letting it run when nobody is there.