Infinite Sweeps

Is it required to read the rules each time you enter a daily sweep?

I have found it very helpful to read them every time for several reasons. 

I look at the dates for every contest I enter. For contests that I enter regularly (like most of the instant win daily entry contests) I append the end date to my bookmark title. 
For single entry contests, I append the drawing date so I know when to check winner's lists and such. 

I also find it very helpful to identify entry limits and alternate entry methods so I don't miss any entries. Very often contests will tell you what email address a winning notification will come from, so I can immediately add it to my gmail filter for wins. 

A lot of sweeps use similar platforms so reading the rules becomes easier the more you do it. After reading through enough of them, you'll be able to scan through them faster. 

Also, keeping the link to the rules for each contest log in my spreadsheet makes it easy to reference later.  

As far as being "required" is concerned, no. It's not required. However, when you check the box that says you have read the rules, even if you haven't read them, you are bound by them.