If you have never used sheet protectors with white board markers in the classroom, I have to tell you it is a must, or at least it is in my 1st grade classroom. I'm not really a worksheet person anyways, but when I give worksheets I want them to really be worth the time. Using sheet protectors allows me to: 1) make fewer copies, and 2) reuse them over and over for additional practice. It is not to say that I never give paper and pencil worksheets, I just use sheet protectors whenever it makes more sense.
I especially love using sheet protectors to make reusable workbooks for a center activity. I put worksheets in sheet protectors and then I place them in a three pronged folder or staple them in a sheet of construction paper. Some of the books I have made have lasted several years. Here is a picture of some examples.
I use sheet protectors for math practice, assessment review, comprehension pages, sentence practice folders, writing organizers, Word Wall practice activities, and individual practice sheets. I have used sheet protectors for the past 13 years and I love them. There have been a couple of draw backs though. The first big one is that white board markers can be expensive when you are buying a whole class set, plus extras. Here is what I have done to work around this: 1) ask for parent donations; 2) purchase from the Dollar or 99 Cent Store; and 3) stock up at the beginning of the year during Back-to-School sales. I recommend ONLY using black white board markers. The other colors tend to stain. Also, make sure to train students on how to use the white board markers without destroying them (i.e., don't push too hard, don't lose the cap, cap up marker).
The other problem that I had, which wasn't much of a problem, just more time consuming, was changing out individual sheets. For example, this year I am using a CAT Facts math practice sheet, number writing, Black Bean Activities, and my Roll and Add game. Putting all those activities in sheet protector/changing them out can be a bit of a hassle. This year I had my students purchase reusable pockets from Lakeshore Teaching supply, plus I purchased 10 extra. This gave everyone their own pocket. These pockets are more kid friendly and students can change or switch papers on their own.
As I have already mentioned, I love using sheet protectors. I recommend that you try them if you have never used them before. You don' have to start big, just try it with a small group and see how it works for you.