Both your arguments share one feature: rapid iterations. It's much easier to iterate over various cancer factors/treatments/conditions when the duration of a si

Both your arguments share one feature: rapid iterations. It's much easier to iterate over various cancer factors/treatments/conditions when the duration of a single mouse experiment is in the range of maybe 6 months. But when you want a mouse to live for 10 years your iterations take 10 years. And you cannot do the research anymore with PhD students or postdocs because they aren't with you for long enough. A problem that actually arises right now in organoid research as human organs, for some reason, need in the order of 9 months to fully develop. And 9 months plus learning, experimental planning, analysis and thesis writing gets you uncomfortable close to the 3-4 years a PhD typically takes (or at least doesn't allow much back and forth iterating).