I took a couple of classes about that long that were terrific.

One was a vim thing by Damian Conway at OSCon 2006(?) and the other was a very fast-paced Linux kernel programming class by Greg Kroah-Hartman at Oregon State. The knowledge from both have stuck with me decade(s) later.

I feel like if you have a good instructor and have a few hours of isolation, you can have some seriously productive learning. Or at least, I can.