I've not been going at anywhere near the same rate as you, but I've been doing self-directed study for the past few years. This year I made an ongoing pledge to read an undergrad textbook on every subject I claim to have an interest in. Abe Books has been pretty useful here, and it's possible to pick up a wealth of respectable textbooks at a very agreeable price if you're happy with a slightly older version. The importance of the textbook's age obviously varies from subject to subject, but a lot of introductory material for established subjects ages quite well.

Having a learning buddy seems very useful, but a lot easier to orchestrate when following some sort of designated syllabus such as the MIRI course list. This seems like quite a strong argument for producing and following such a syllabus.