I allways keep the psd (or atleast try to) coz a lot of times i get a task that's allmost the same as a previous personal project, and i can just modify the old psd
or like my wallpaper. It's the logo's/mascots of the bands i'm gonna see. but that list might change, so i keep the psd. also i keep all teh stuff inside the png vectorized so i can resize them or edit the style, shadows and stuff without losing anything
look:

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