Once the action is written it will always be there to use each time you open photoshop. By doing it as percentage it scales to any size or layout. If you ever want to delete one then you grab it and drag it to the trash can.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html