Way to keep lettuce fresh

Hi. I found these bags (green plastic) that absorb the gas that ripens fruit. What I do is buy whatever lettuce is on sale and rip up (not cut) the entire head at once, wash and toss in the bag. I don't even tie it up, just keep it in my vegtable bin. I add whatever ingredients to each portion I take out during the week. These bags have kept lettuce fresh from a sunday to a sunday. They are wonderful and I did not have to throw out any of the lettuce. It all got used Hope you can find these, they are great.