If I understood correctly from the GTD readings also a

someday

list or vault needs to be reviewed regularly. The main difference between it and your projects or active interests is that it carries no obligation to achieve or close anything. I use this approach to fight being overwhelmed with things to do or learn: putting topics deliberately on that list gives me the freedom to feel good about ignoring them for now while I pursue something else or simply need to work on other stuff. This doesn't answer your question on specialist vs. generalist though