I’m not setting boundaries - and I think you will notice when to shift! When noone and no book seems to teach you anything new about a certain topic. When you read the latest book and think, „hmm yes, but i think they omitted a and b and c and in reality this isn’t so nicely separated and way more nuanced“. Then it is definitely time to shift your attention to a different topic. I’m doing this for decades now - and i think lots of others too. You will never learn all about everything. But it’s fun to try :-)