For me, having multiple runtimes attached is a way to have fewer books on my desk, not more.

I have runtimes devoted to particular figures, as well as particular subjects. SF, fantasy, contemporary, horror, politics, etc. If I'm working on a political cartoon, I probably don't need Vicky's fantasy brass bikinis, so I don't attach that runtime. If I'm working on a historical image, I don't need the SF or contemporary runtimes.

At this point, the problem isn't really hardware, it's wetware. Multiple runtimes help me remember where things are. Searching doesn't always work, because I remember what I want, but not what it was called.