Why do scientists receive multiple-year grants when many other things are reviewed each year and funding is given out for smaller time intervals?

When you are focused on your work, what happens when someone distracts you? You may lose your place in a book that you are reading. Your understanding of what you read may go down because of the time interval between reading one section and another is lengthened and you lost your train of thought. Say you were eating and had to run out to do something with little warning.The food could go bad (if you can't preserve it) and you would need to get new food when you finally sit down to eat again. Ultimately, you can't get as much done or help as many people.

This is what happens in science. Researchers are forced to do different things and can become "rusty" on what they had been doing. When I say "do different things", I do not necessarily mean that they would just do more research. Researchers are not able to take on as many projects and train as many students. This has ripple effects across generations. On a shorter term, researchers can't just resume the research that they had stopped. The students previously working on projects graduate and the flow of information between senior to junior students is stifled. It costs money to re-train students on topics. Reagents go bad and need to be purchased again, adding additional expense.

Also, scientists are required to report on their progress and their programs do come up for review just like other programs.