[a1a]

I'd recommend deleting all content associated with the account and removing the address from any third party site (recovery etc).

I would however never actually delete the account.

My concern with deleting the account is that it exposes you to some really nasty impersonation attacks. It is free to keep. Just keep it.

[home_boi]

I agree. The act of deleting the account isn't even a guarantee that the data associated with the account will be deleted.

[ma2rten]

I don't know about Yahoo, but most services will not allow to reregister a previously deleted account.

[JustSomeNobody]

I vaguely recall that yahoo does recycle old email addresses.