It is important to have your campaign working at its best if you want to make money in this business.
Each month you should check your words and see which are a waist of time and which are worth keeping.
If they of no use to you take it out and look for a better performing one.
Its quite possible that as you get more advanced with your campaign you will be deleting keywords or move them to an alternate ad groups or campaign.
It all depends on how you want to maintain your campaign history with the Adword Editor.
Adwords is really helpful in that it helps maintain our account history and any time you do a little Adword maintenance yourself it will help with the maintenance of your account history.
And for those who have had their accounts for a while, you will be happy to know that AdWords recognizes you.
A couple of other facts , the movement of keywords will not affect your performance history and you can get with this by using Google's optimization tool.
It helps move keywords from one ad group to another.
Just a word of caution with your campaign, if you plan to remove or delete some keywords be aware that it can affect your performance history.
And possibly damage your account to the extent of removing that history.
It's a fact that deleting keywords has a couple of good things about it.
First of all it prevents new impressions of your ad.
If the keyword has not been doing so well they could drag down your Click through Rate of your entire campaign.
And secondly while erasing certain history may be good for a nice clean start not all history is deleted.