Before revision: Although 241Am has a half-life of 432 years which is more than 238Pu and could hypothetically power a device for centuries, missions with more than 10 years were not the subject of the research until 2019.
After revision: Although 241Am has a half-life of 432 years , which is about five times longer than that of 238Pu and could hypothetically power a device for centuries, missions with more than 10 years were not the subject of the research until 2019.