I would strongly suggest you get anything you can done as soon as possible, as long as you don't sacrifice quality. As far as those things which involve teachers, I can tell you that evaluations and letters of recommendation can be extremely difficult to get once school is out. Teachers become instantly unavailable once summer starts, and tend not to respond to emails. It can be very frustrating. I highly recommend you get that stuff out, and then talk to your teachers about it daily until you see on your portal that it is done.
Some will tell you that there is no advantage to getting things in early. I will just say that if you get things done now you can check it off the long list. Most items can be improved upon and updated, so there is no harm getting it in early. So many components of the application process are out of your control. It is good to complete the stuff that you do control. No time like the present.