As a designer, you tend to be involved with many logos over time, both your own and others. Everyone and their sister’s lesbian roommate’s cousin has a logo, and you will eventually probably use them in some project. And if you have any sense at all, you back up all the art from your projects anyway. But I recommend keeping a logo archive, preferably in a convenient location for immediate use. Logos, when done right, are very small files, so they won’t take up much space. Not a week goes by that I don’t go back to my archive to pull up a logo. If it would otherwise take 5 minutes to dig up the right file, that’s a savings of over 4 hours, over the course of a year. But most importantly, it will inevitably improve the quality of your work. It never ceases to amaze me how many companies — large or small — can’t provide you good copies of their logos. By saving the best copy you can find of everyone’s logo, your work improves and you exceed your client’s expectations.