It depends on what you study. I did Engineering so I will speak from that perspective.
Take as many prerequisites as you can outside of Umich. You can cover these by taking classes at a community college and AP tests. You can also receive credits by doing well on a language placement test (they were generous with the granting of credit for the Spanish test when I took it). This will save you time and money. It will also probably be easier to register for classes (registration is based on credits). I recommend having transfer/test credit for as many of the following as you can:
-MATH 115, 116, 215, 216
-CHEM 125/126, 130
-Physics 140,141,240,241
-ENGR 101
-Intellectual Breadth (AP tests that do not cover the above will probably be able to count in this area)
In terms of graduating early, it depends. I am not in the “stay because it is the time of your life” boat. Yes, there are enjoyable moments in college. However, I think you can have enough enjoyable moments in 6 or 7 semesters (graduating a year or half year early). You will get tired of homework, group projects (oh you will get upset with group projects), and boring lectures. You will probably get to a point in Junior or Senior year where you are like “can I just get my degree already?” You will probably not miss homework, group projects, and boring lectures if you are working at a job you enjoy, making good money, and enjoying life outside of work.
However, I do NOT recommend taking an ultra heavy course load each semester such that it makes your life miserable. It is probably not worth it. However, you can still graduate early without taking an ultra heavy course load.
Additionally, it depends on if you want to do a Masters. If you want to do a Masters and someone will give you a grad student appointment of 25% or more, then graduate early. As a GSI/GSRA/GSSA (forms of graduate student appointments) you get tuition waived and a monthly stipend!
If you want to do a Masters, but cannot get a grad student appointment, do NOT graduate early. Instead, take classes you would normally take as a grad student and get at least a B in those courses for a semester. The following semester, start grad school. You can transfer/double count courses you took in undergrad to grad. You can transfer up to 15 credits. This would allow you to do a Masters in one heavy semester (15 credits is a lot for Masters) or 2 doable semesters (8 in one and 7 in the other). Keep in mind that a Masters is a lot more expensive per semester (assuming no grad student appointment).
In general, I would recommend graduating early or taking a semester off to do a co-op. You will save time and money. You will probably be able to start working earlier (assuming you get a job). You will not miss the homework. You will not miss late nights doing a bunch of school work. You will probably be a lot happier with your work life balance outside after graduating.