How much vacation time could you theoretically take in the various subspecialties, working in academia vs. private practice? Let's say, taking cardio, pulm, heme/onc, rheum, ID, and endocrine into consideration.

Theoretically, it sounds like you should be able to block off certain weeks of the year that you're off, but I could imagine some specialties (e.g. cardio, pulm, heme/onc) throwing emergencies and complications at unexpected times so you couldn't be away from work for more than a few days unless someone else stepped in for you, which might not be OK/practical in certain cases.

So this is not so much a question of what's typically done or what employers allow, but rather what sort of time constraints the work itself imposes.