I've found that a ramification of holding the current program in my head is that I have a greater emotional bond with whatever problem I've most recently worked on.

If I work on several project concurrently, there's always one of them that I am more passionate about at any given time, causing me to think about it at nearly all hours of the day. Interestingly, the one I am more passionate about oscillates -- and is nearly always the project I have most recently worked on for a large chunk of time. Therefore, it is the one in which I am holding the most context in my head.