Do you notice that when you buy fresh parsley or any other bunch of fresh herbs at the grocer they begin to wilt before you are able to use the entire bunch?
Firstly, to make fresh herbs last longer, don't wash them immediately. Refrigerate and wash only what you need just prior to using. Another way to get the most from store bought or even home grown herbs is to dry them.
If you have a large bunch and know that you won't be able to use the entire bunch by the end of the week just clip off half the bunch to dry and the other half put in the fridge to use as fresh greenery -garnish. You can dry herbs in the oven on a low temp or use an electric counter top fruit/veggie dryer (not a hair dryer) ;-).
This frugal tip also applies to any fresh fruits and or veggies that you see beginning to lose their zest, their crispiness. Wash, peel and cut or dice/slice them up to dry in the over or electric counter top fruit/veggie dryer which store longer and can be used for future soups or salads...even dipped in chocolate!