Like mentioned before, you can always buy just egg whites from the store. Egg Beaters are made of just the white plus they add in vitamins...personally however I think they taste like shit. Fresh non pastuerized egg whites taste better to me and I think the prices are sort of rediculous.
I'm in the same boat because I eat around a dozen egg whites a day (love em) but in all honesty it doesn't take too long to crack em open with each meal.
If you are going to be eating the eggs whites quickly, I think they would be fine for a few days in the fridge. But if you want the conveinance and not having to worry about bacteria then I would just buy some pasteurized egg whites. You can always buy the huge tubs of egg whites from places like http://www.eggwhitesint.com/
instead of buying the small ones at the stores. Since you only get 4 grams of protein per egg white, this maybe a good option if you eat alot of them.