Not to mention that abandoned github repos wind up in google searches and I have learned something from looking at them in such a context, even if untouched for

Not to mention that abandoned github repos wind up in google searches and I have learned something from looking at them in such a context, even if untouched for years. Don't delete your repos because they are "old". You could be doing a favor for some random person with a google search, looking at something you looked at too.