Store away!!! Just remember, backing up is next to cleanliness (or godliness, I can never remember). I use old drives all the time, and as long as you have good airflow in your case (high temps kill HDDs, too) they should give you good service. But please, please, backup once a week, or even better, install a backup HDD in your case and use settings->Update & Security->Backup to set up automatic backups. Make sure "Automatically back up my files" is turned on, the click on "more options". Tell it how often you want it to back up your files (I use the default "Every Hour"), then select the drives/folders/files you want to backup. Finally, select the backup drive target.